diff --git a/jso/apis/src/main/java/org/teavm/jso/crypto/Crypto.java b/jso/apis/src/main/java/org/teavm/jso/crypto/Crypto.java
index b435c01ab..3a5a00cab 100644
--- a/jso/apis/src/main/java/org/teavm/jso/crypto/Crypto.java
+++ b/jso/apis/src/main/java/org/teavm/jso/crypto/Crypto.java
@@ -17,6 +17,8 @@ package org.teavm.jso.crypto;
 
 import org.teavm.jso.JSBody;
 import org.teavm.jso.JSObject;
+import org.teavm.jso.JSProperty;
+import org.teavm.jso.JSTopLevel;
 import org.teavm.jso.typedarrays.Int16Array;
 import org.teavm.jso.typedarrays.Int32Array;
 import org.teavm.jso.typedarrays.Int8Array;
@@ -28,7 +30,8 @@ public abstract class Crypto implements JSObject {
     @JSBody(script = "return crypto != null;")
     public static native boolean isSupported();
 
-    @JSBody(script = "return crypto;")
+    @JSProperty("crypto")
+    @JSTopLevel
     public static native Crypto current();
 
     public abstract String randomUUID();
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAnchorElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAnchorElement.java
index 20ddd6660..b221f7fab 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAnchorElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAnchorElement.java
@@ -18,55 +18,55 @@ package org.teavm.jso.dom.html;
 import org.teavm.jso.JSProperty;
 import org.teavm.jso.dom.types.DOMTokenList;
 
-public interface HTMLAnchorElement extends HTMLElement {
+public abstract class HTMLAnchorElement extends HTMLElement {
     @JSProperty
-    String getHref();
+    public abstract String getHref();
 
     @JSProperty
-    void setHref(String value);
+    public abstract void setHref(String value);
 
     @JSProperty
-    String getTarget();
+    public abstract String getTarget();
 
     @JSProperty
-    void setTarget(String value);
+    public abstract void setTarget(String value);
 
     @JSProperty
-    String getRel();
+    public abstract String getRel();
 
     @JSProperty
-    void setRel(String value);
+    public abstract void setRel(String value);
 
     @JSProperty
-    DOMTokenList getTokenList();
+    public abstract DOMTokenList getTokenList();
 
     @JSProperty
-    String getMedia();
+    public abstract String getMedia();
 
     @JSProperty
-    void setMedia(String value);
+    public abstract void setMedia(String value);
 
     @JSProperty
-    String getHreflang();
+    public abstract String getHreflang();
 
     @JSProperty
-    void setHreflang(String value);
+    public abstract void setHreflang(String value);
 
     @JSProperty
-    String getType();
+    public abstract String getType();
 
     @JSProperty
-    void setType(String value);
+    public abstract void setType(String value);
 
     @JSProperty
-    String getText();
+    public abstract String getText();
 
     @JSProperty
-    void setText(String value);
+    public abstract void setText(String value);
 
     @JSProperty
-    String getDownload();
+    public abstract String getDownload();
 
     @JSProperty
-    void setDownload(String download);
+    public abstract void setDownload(String download);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAudioElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAudioElement.java
index 0d6ebd15e..67365a68c 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAudioElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLAudioElement.java
@@ -15,10 +15,5 @@
  */
 package org.teavm.jso.dom.html;
 
-/**
- *
- * @author Junji Takakura
- */
-public interface HTMLAudioElement extends HTMLMediaElement {
-
+public abstract class HTMLAudioElement extends HTMLMediaElement {
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBaseElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBaseElement.java
index a0bc87cd2..3c473fae7 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBaseElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBaseElement.java
@@ -17,15 +17,15 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLBaseElement extends HTMLElement {
+public abstract class HTMLBaseElement extends HTMLElement {
     @JSProperty
-    String getHref();
+    public abstract String getHref();
 
     @JSProperty
-    void setHref(String href);
+    public abstract void setHref(String href);
 
     @JSProperty
-    String getTarget();
+    public abstract String getTarget();
 
-    void setTarget(String target);
+    public abstract void setTarget(String target);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBodyElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBodyElement.java
index 9f9c94143..360ace9b4 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBodyElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLBodyElement.java
@@ -19,26 +19,26 @@ import org.teavm.jso.JSProperty;
 import org.teavm.jso.dom.events.Event;
 import org.teavm.jso.dom.events.EventListener;
 
-public interface HTMLBodyElement extends HTMLElement {
+public abstract class HTMLBodyElement extends HTMLElement {
     @JSProperty("onbeforeunload")
-    void setOnBeforeUnload(EventListener<Event> listener);
+    public abstract void setOnBeforeUnload(EventListener<Event> listener);
 
     @JSProperty("onerror")
-    void setOnError(EventListener<Event> listener);
+    public abstract void setOnError(EventListener<Event> listener);
 
     @JSProperty("onload")
-    void setOnLoad(EventListener<Event> listener);
+    public abstract void setOnLoad(EventListener<Event> listener);
 
     @JSProperty("onmessage")
-    void setOnMessage(EventListener<Event> listener);
+    public abstract void setOnMessage(EventListener<Event> listener);
 
     @JSProperty("onoffline")
-    void setOnOffline(EventListener<Event> listener);
+    public abstract void setOnOffline(EventListener<Event> listener);
 
     @JSProperty("ononline")
-    void setOnOnline(EventListener<Event> listener);
+    public abstract void setOnOnline(EventListener<Event> listener);
 
     @JSProperty("ononunload")
-    void setOnUnload(EventListener<Event> listener);
+    public abstract void setOnUnload(EventListener<Event> listener);
 }
 
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLButtonElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLButtonElement.java
index f549b77c2..061a3e68d 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLButtonElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLButtonElement.java
@@ -17,43 +17,43 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLButtonElement extends HTMLElement {
-    String TYPE_BUTTON = "button";
+public abstract class HTMLButtonElement extends HTMLElement {
+    public static final String TYPE_BUTTON = "button";
 
-    String TYPE_RESET = "reset";
+    public static final String TYPE_RESET = "reset";
 
-    String TYPE_SUBMIT = "submit";
+    public static final String TYPE_SUBMIT = "submit";
 
     @JSProperty
-    boolean isAutofocus();
+    public abstract boolean isAutofocus();
 
     @JSProperty
-    void setAutofocus(boolean autofocus);
+    public abstract void setAutofocus(boolean autofocus);
 
     @JSProperty
-    boolean isDisabled();
+    public abstract boolean isDisabled();
 
     @JSProperty
-    void setDisabled(boolean disabled);
+    public abstract void setDisabled(boolean disabled);
 
     @JSProperty
-    HTMLElement getForm();
+    public abstract HTMLElement getForm();
 
     @JSProperty
-    String getName();
+    public abstract String getName();
 
     @JSProperty
-    void setName(String name);
+    public abstract void setName(String name);
 
     @JSProperty
-    String getValue();
+    public abstract String getValue();
 
     @JSProperty
-    void setValue(String value);
+    public abstract void setValue(String value);
 
     @JSProperty
-    String getType();
+    public abstract String getType();
 
     @JSProperty
-    void setType(String type);
+    public abstract void setType(String type);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLCanvasElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLCanvasElement.java
index 79cac70ed..6f14bb5e6 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLCanvasElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLCanvasElement.java
@@ -19,26 +19,26 @@ import org.teavm.jso.JSObject;
 import org.teavm.jso.JSProperty;
 import org.teavm.jso.canvas.CanvasImageSource;
 
-public interface HTMLCanvasElement extends HTMLElement, CanvasImageSource {
+public abstract class HTMLCanvasElement extends HTMLElement implements CanvasImageSource {
     @JSProperty
-    int getWidth();
+    public abstract int getWidth();
 
     @JSProperty
-    void setWidth(int width);
+    public abstract void setWidth(int width);
 
     @JSProperty
-    int getHeight();
+    public abstract int getHeight();
 
     @JSProperty
-    void setHeight(int height);
+    public abstract void setHeight(int height);
 
-    JSObject getContext(String contextId);
+    public abstract JSObject getContext(String contextId);
 
-    JSObject getContext(String contextId, JSObject attributes);
+    public abstract JSObject getContext(String contextId, JSObject attributes);
 
-    String toDataURL(String type, double quality);
+    public abstract String toDataURL(String type, double quality);
 
-    String toDataURL(String type);
+    public abstract String toDataURL(String type);
 
-    String toDataURL();
+    public abstract String toDataURL();
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLDocument.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLDocument.java
index 1e09572ab..f78644557 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLDocument.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLDocument.java
@@ -22,74 +22,74 @@ import org.teavm.jso.dom.events.EventTarget;
 import org.teavm.jso.dom.xml.Document;
 import org.teavm.jso.dom.xml.NodeList;
 
-public interface HTMLDocument extends Document, EventTarget {
+public abstract class HTMLDocument implements Document, EventTarget {
     @JSProperty
     @Override
-    HTMLHtmlElement getDocumentElement();
+    public abstract HTMLHtmlElement getDocumentElement();
 
     @Override
-    HTMLElement createElement(String tagName);
+    public abstract HTMLElement createElement(String tagName);
 
-    default HTMLElement createElement(String tagName, Consumer<HTMLElement> consumer) {
+    public final HTMLElement createElement(String tagName, Consumer<HTMLElement> consumer) {
         HTMLElement result = createElement(tagName);
         consumer.accept(result);
         return result;
     }
 
     @Override
-    HTMLElement getElementById(String elementId);
+    public abstract HTMLElement getElementById(String elementId);
 
     @JSProperty
-    HTMLBodyElement getBody();
+    public abstract HTMLBodyElement getBody();
 
     @JSProperty
-    HTMLHeadElement getHead();
+    public abstract HTMLHeadElement getHead();
 
     @JSProperty
-    int getScrollLeft();
+    public abstract int getScrollLeft();
 
     @JSProperty
-    int getScrollTop();
+    public abstract int getScrollTop();
 
-    static HTMLDocument current() {
+    public static HTMLDocument current() {
         return Window.current().getDocument();
     }
 
     @Override
-    HTMLElement querySelector(String selectors);
+    public abstract HTMLElement querySelector(String selectors);
 
     @Override
-    NodeList<? extends HTMLElement> querySelectorAll(String selectors);
+    public abstract NodeList<? extends HTMLElement> querySelectorAll(String selectors);
 
     @JSProperty
-    HTMLElement getActiveElement();
+    public abstract HTMLElement getActiveElement();
 
-    HTMLElement elementFromPoint(int x, int y);
+    public abstract HTMLElement elementFromPoint(int x, int y);
 
     @JSProperty
-    boolean isDesignMode();
+    public abstract boolean isDesignMode();
 
     @JSProperty
-    void setDesignMode(boolean value);
+    public abstract void setDesignMode(boolean value);
 
-    void execCommand(String commandName, boolean showDefaultUI, String valueArgument);
+    public abstract void execCommand(String commandName, boolean showDefaultUI, String valueArgument);
 
-    void execCommand(String commandName);
+    public abstract void execCommand(String commandName);
 
     @JSProperty
-    String getCookie();
+    public abstract String getCookie();
 
     @JSProperty
-    void setCookie(String cookie);
+    public abstract void setCookie(String cookie);
 
     @JSProperty
-    String getTitle();
+    public abstract String getTitle();
 
     @JSProperty
-    void setTitle(String title);
+    public abstract void setTitle(String title);
 
     @JSProperty
-    HTMLElement getPointerLockElement();
+    public abstract HTMLElement getPointerLockElement();
 
-    void exitPointerLock();
+    public abstract void exitPointerLock();
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLElement.java
index 3e627f76c..b40546484 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLElement.java
@@ -29,158 +29,158 @@ import org.teavm.jso.dom.xml.Element;
 import org.teavm.jso.dom.xml.Node;
 import org.teavm.jso.dom.xml.NodeList;
 
-public interface HTMLElement extends Element, ElementCSSInlineStyle, EventTarget, FocusEventTarget, MouseEventTarget,
-        WheelEventTarget, KeyboardEventTarget, LoadEventTarget {
+public abstract class HTMLElement implements Element, ElementCSSInlineStyle, EventTarget, FocusEventTarget,
+        MouseEventTarget, WheelEventTarget, KeyboardEventTarget, LoadEventTarget {
     @Override
-    NodeList<? extends HTMLElement> getElementsByTagName(String name);
+    public abstract NodeList<? extends HTMLElement> getElementsByTagName(String name);
 
     @JSProperty
-    String getTitle();
+    public abstract String getTitle();
 
     @JSProperty
-    void setTitle(String title);
+    public abstract void setTitle(String title);
 
     @JSProperty
-    String getLang();
+    public abstract String getLang();
 
     @JSProperty
-    void setLang(String lang);
+    public abstract void setLang(String lang);
 
     @JSProperty
-    boolean isTranslate();
+    public abstract boolean isTranslate();
 
     @JSProperty
-    void setTranslate(boolean translate);
+    public abstract void setTranslate(boolean translate);
 
     @JSProperty
-    String getDir();
+    public abstract String getDir();
 
     @JSProperty
-    void setDir(String dir);
+    public abstract void setDir(String dir);
 
     @JSProperty
-    boolean isHidden();
+    public abstract boolean isHidden();
 
     @JSProperty
-    void setHidden(boolean hidden);
+    public abstract void setHidden(boolean hidden);
 
-    void click();
+    public abstract void click();
 
     @JSProperty
-    int getTabIndex();
+    public abstract int getTabIndex();
 
     @JSProperty
-    void setTabIndex(int tabIndex);
+    public abstract void setTabIndex(int tabIndex);
 
-    void focus();
+    public abstract void focus();
 
-    void blur();
+    public abstract void blur();
 
     @JSProperty
-    String getAccessKey();
+    public abstract String getAccessKey();
 
     @JSProperty
-    void setAccessKey(String accessKey);
+    public abstract void setAccessKey(String accessKey);
 
     @JSProperty
-    String getAccessKeyLabel();
+    public abstract String getAccessKeyLabel();
 
     @JSProperty
-    int getClientWidth();
+    public abstract int getClientWidth();
 
     @JSProperty
-    int getClientHeight();
+    public abstract int getClientHeight();
 
     @JSProperty
-    int getAbsoluteLeft();
+    public abstract int getAbsoluteLeft();
 
     @JSProperty
-    int getAbsoluteTop();
+    public abstract int getAbsoluteTop();
 
     @JSProperty
-    int getScrollLeft();
+    public abstract int getScrollLeft();
 
     @JSProperty
-    void setScrollLeft(int scrollLeft);
+    public abstract void setScrollLeft(int scrollLeft);
 
     @JSProperty
-    int getScrollTop();
+    public abstract int getScrollTop();
 
     @JSProperty
-    void setScrollTop(int scrollTop);
+    public abstract void setScrollTop(int scrollTop);
 
     @JSProperty
-    int getScrollWidth();
+    public abstract int getScrollWidth();
 
     @JSProperty
-    int getScrollHeight();
+    public abstract int getScrollHeight();
 
     @JSProperty
-    int getOffsetWidth();
+    public abstract int getOffsetWidth();
 
     @JSProperty
-    int getOffsetHeight();
+    public abstract int getOffsetHeight();
 
     @JSProperty
-    int getOffsetTop();
+    public abstract int getOffsetTop();
 
     @JSProperty
-    int getOffsetLeft();
+    public abstract int getOffsetLeft();
 
     @JSProperty
     @Override
-    HTMLDocument getOwnerDocument();
+    public abstract HTMLDocument getOwnerDocument();
 
     @JSProperty
-    HTMLCollection getChildren();
+    public abstract HTMLCollection getChildren();
 
     @JSProperty
-    String getInnerHTML();
+    public abstract String getInnerHTML();
 
     @JSProperty
-    void setInnerHTML(String content);
+    public abstract void setInnerHTML(String content);
 
     @JSProperty
-    String getInnerText();
+    public abstract String getInnerText();
 
     @JSProperty
-    void setInnerText(String content);
+    public abstract void setInnerText(String content);
 
-    TextRectangle getBoundingClientRect();
+    public abstract TextRectangle getBoundingClientRect();
 
     @JSProperty
-    String getClassName();
+    public abstract String getClassName();
 
     @JSProperty
-    void setClassName(String className);
+    public abstract void setClassName(String className);
 
     @JSProperty
-    DOMTokenList getClassList();
+    public abstract DOMTokenList getClassList();
 
-    default HTMLElement withAttr(String name, String value) {
+    public final HTMLElement withAttr(String name, String value) {
         setAttribute(name, value);
         return this;
     }
 
-    default HTMLElement withChild(String tagName) {
+    public final HTMLElement withChild(String tagName) {
         HTMLElement result = getOwnerDocument().createElement(tagName);
         appendChild(result);
         return this;
     }
 
-    default HTMLElement withChild(Node node) {
+    public final HTMLElement withChild(Node node) {
         appendChild(node);
         return this;
     }
 
-    default HTMLElement withChild(String tagName, Consumer<HTMLElement> consumer) {
+    public final HTMLElement withChild(String tagName, Consumer<HTMLElement> consumer) {
         HTMLElement result = getOwnerDocument().createElement(tagName);
         appendChild(result);
         consumer.accept(result);
         return this;
     }
 
-    default HTMLElement clear() {
+    public final HTMLElement clear() {
         Node node = getLastChild();
         while (node != null) {
             Node prev = node.getPreviousSibling();
@@ -192,16 +192,16 @@ public interface HTMLElement extends Element, ElementCSSInlineStyle, EventTarget
         return this;
     }
 
-    default HTMLElement withText(String content) {
+    public final HTMLElement withText(String content) {
         clear().appendChild(getOwnerDocument().createTextNode(content));
         return this;
     }
 
     @Override
-    HTMLElement querySelector(String selectors);
+    public abstract HTMLElement querySelector(String selectors);
 
     @Override
-    NodeList<? extends HTMLElement> querySelectorAll(String selectors);
+    public abstract NodeList<? extends HTMLElement> querySelectorAll(String selectors);
 
-    void requestPointerLock();
+    public abstract void requestPointerLock();
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLFormElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLFormElement.java
index 863527006..b6f6f465e 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLFormElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLFormElement.java
@@ -18,73 +18,73 @@ package org.teavm.jso.dom.html;
 import org.teavm.jso.JSIndexer;
 import org.teavm.jso.JSProperty;
 
-public interface HTMLFormElement extends HTMLElement {
+public abstract class HTMLFormElement extends HTMLElement {
     @JSProperty
-    String getAcceptCharset();
+    public abstract String getAcceptCharset();
 
     @JSProperty
-    void setAcceptCharset(String value);
+    public abstract void setAcceptCharset(String value);
 
     @JSProperty
-    String getAction();
+    public abstract String getAction();
 
     @JSProperty
-    void setAction(String value);
+    public abstract void setAction(String value);
 
     @JSProperty
-    String getAutocomplete();
+    public abstract String getAutocomplete();
 
     @JSProperty
-    void setAutocomplete(String value);
+    public abstract void setAutocomplete(String value);
 
     @JSProperty
-    String getEnctype();
+    public abstract String getEnctype();
 
     @JSProperty
-    void setEnctype(String enctype);
+    public abstract void setEnctype(String enctype);
 
     @JSProperty
-    String getEncoding();
+    public abstract String getEncoding();
 
     @JSProperty
-    void setEncoding(String value);
+    public abstract void setEncoding(String value);
 
     @JSProperty
-    String getMethod();
+    public abstract String getMethod();
 
     @JSProperty
-    void setMethod(String value);
+    public abstract void setMethod(String value);
 
     @JSProperty
-    String getName();
+    public abstract String getName();
 
     @JSProperty
-    void setName(String name);
+    public abstract void setName(String name);
 
     @JSProperty
-    boolean isNoValidate();
+    public abstract boolean isNoValidate();
 
     @JSProperty
-    void setNoValidate(boolean value);
+    public abstract void setNoValidate(boolean value);
 
     @JSProperty
-    String getTarget();
+    public abstract String getTarget();
 
     @JSProperty
-    void setTarget(String value);
+    public abstract void setTarget(String value);
 
     @JSIndexer
-    HTMLElement get(String name);
+    public abstract HTMLElement get(String name);
 
     @JSIndexer
-    HTMLElement get(int index);
+    public abstract HTMLElement get(int index);
 
     @JSProperty
-    int getLength();
+    public abstract int getLength();
 
-    void submit();
+    public abstract void submit();
 
-    void reset();
+    public abstract void reset();
 
-    boolean checkValidity();
+    public abstract boolean checkValidity();
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHeadElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHeadElement.java
index 57c97e786..679a75214 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHeadElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHeadElement.java
@@ -15,5 +15,5 @@
  */
 package org.teavm.jso.dom.html;
 
-public interface HTMLHeadElement extends HTMLElement {
+public abstract class HTMLHeadElement extends HTMLElement {
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHtmlElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHtmlElement.java
index f6365886d..8039d6f46 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHtmlElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLHtmlElement.java
@@ -15,5 +15,5 @@
  */
 package org.teavm.jso.dom.html;
 
-public interface HTMLHtmlElement extends HTMLElement {
+public abstract class HTMLHtmlElement extends HTMLElement {
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLIFrameElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLIFrameElement.java
index 959b80377..4419d29a6 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLIFrameElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLIFrameElement.java
@@ -18,40 +18,40 @@ package org.teavm.jso.dom.html;
 import org.teavm.jso.JSProperty;
 import org.teavm.jso.browser.Window;
 
-public interface HTMLIFrameElement extends HTMLElement {
+public abstract class HTMLIFrameElement extends HTMLElement {
     @JSProperty
-    HTMLDocument getContentDocument();
+    public abstract HTMLDocument getContentDocument();
 
     @JSProperty
-    Window getContentWindow();
+    public abstract Window getContentWindow();
 
     @JSProperty
-    String getWidth();
+    public abstract String getWidth();
 
     @JSProperty
-    void setWidth(String width);
+    public abstract void setWidth(String width);
 
     @JSProperty
-    String getHeight();
+    public abstract String getHeight();
 
     @JSProperty
-    void setHeight(String height);
+    public abstract void setHeight(String height);
 
     @JSProperty
-    String getName();
+    public abstract String getName();
 
     @JSProperty
-    void setName(String name);
+    public abstract void setName(String name);
 
     @JSProperty("src")
-    String getSourceAddress();
+    public abstract String getSourceAddress();
 
     @JSProperty("src")
-    void setSourceAddress(String src);
+    public abstract void setSourceAddress(String src);
 
     @JSProperty("srcdoc")
-    String getSourceDocument();
+    public abstract String getSourceDocument();
 
     @JSProperty("srcdoc")
-    void setSourceDocument(String srcdoc);
+    public abstract void setSourceDocument(String srcdoc);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLImageElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLImageElement.java
index 971443cb9..35236db0d 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLImageElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLImageElement.java
@@ -18,40 +18,40 @@ package org.teavm.jso.dom.html;
 import org.teavm.jso.JSProperty;
 import org.teavm.jso.canvas.CanvasImageSource;
 
-public interface HTMLImageElement extends HTMLElement, CanvasImageSource {
+public abstract class HTMLImageElement extends HTMLElement implements CanvasImageSource {
     @JSProperty
-    String getAlt();
+    public abstract String getAlt();
 
     @JSProperty
-    void setAlt(String alt);
+    public abstract void setAlt(String alt);
 
     @JSProperty
-    int getWidth();
+    public abstract int getWidth();
 
     @JSProperty
-    void setWidth(int width);
+    public abstract void setWidth(int width);
 
     @JSProperty
-    int getHeight();
+    public abstract int getHeight();
 
     @JSProperty
-    void setHeight(int height);
+    public abstract void setHeight(int height);
 
     @JSProperty
-    int getNaturalWidth();
+    public abstract int getNaturalWidth();
 
     @JSProperty
-    int getNaturalHeight();
+    public abstract int getNaturalHeight();
 
     @JSProperty
-    String getSrc();
+    public abstract String getSrc();
 
     @JSProperty
-    void setSrc(String src);
+    public abstract void setSrc(String src);
 
     @JSProperty
-    String getCrossOrigin();
+    public abstract String getCrossOrigin();
 
     @JSProperty
-    void setCrossOrigin(String crossOrigin);
+    public abstract void setCrossOrigin(String crossOrigin);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLInputElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLInputElement.java
index 7b10a273e..cf8f15940 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLInputElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLInputElement.java
@@ -17,66 +17,66 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLInputElement extends HTMLElement {
+public abstract class HTMLInputElement extends HTMLElement {
     @JSProperty
-    boolean isChecked();
+    public abstract boolean isChecked();
 
     @JSProperty
-    void setChecked(boolean checked);
+    public abstract void setChecked(boolean checked);
 
     @JSProperty
-    boolean isDisabled();
+    public abstract boolean isDisabled();
 
     @JSProperty
-    void setDisabled(boolean disabled);
+    public abstract void setDisabled(boolean disabled);
 
     @JSProperty
-    int getMaxLength();
+    public abstract int getMaxLength();
 
     @JSProperty
-    void setMaxLength(int maxLength);
+    public abstract void setMaxLength(int maxLength);
 
     @JSProperty
-    String getName();
+    public abstract String getName();
 
     @JSProperty
-    void setName(String name);
+    public abstract void setName(String name);
 
     @JSProperty
-    boolean isReadOnly();
+    public abstract boolean isReadOnly();
 
     @JSProperty
-    void setReadOnly(boolean readOnly);
+    public abstract void setReadOnly(boolean readOnly);
 
     @JSProperty
-    int getSize();
+    public abstract int getSize();
 
     @JSProperty
-    void setSize(int size);
+    public abstract void setSize(int size);
 
     @JSProperty
-    String getType();
+    public abstract String getType();
 
     @JSProperty
-    void setType(String type);
+    public abstract void setType(String type);
 
     @JSProperty
-    String getValue();
+    public abstract String getValue();
 
     @JSProperty
-    void setValue(String value);
+    public abstract void setValue(String value);
     
-    void setCustomValidity(String validationFailure);
+    public abstract void setCustomValidity(String validationFailure);
     
-    boolean checkValidity();
+    public abstract boolean checkValidity();
     
-    boolean reportValidity();
+    public abstract boolean reportValidity();
 
-    void select();
+    public abstract void select();
 
     @JSProperty
-    String getPlaceholder();
+    public abstract String getPlaceholder();
 
     @JSProperty
-    void setPlaceholder(String value);
+    public abstract void setPlaceholder(String value);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLLinkElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLLinkElement.java
index 8b638e393..0ba1527e2 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLLinkElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLLinkElement.java
@@ -17,40 +17,40 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLLinkElement extends HTMLElement {
+public abstract class HTMLLinkElement extends HTMLElement {
     @JSProperty
-    String getHref();
+    public abstract String getHref();
 
     @JSProperty
-    void setHref(String href);
+    public abstract void setHref(String href);
 
     @JSProperty
-    String getCrossOrigin();
+    public abstract String getCrossOrigin();
 
     @JSProperty
-    void setCrossOrigin(String crossOrigin);
+    public abstract void setCrossOrigin(String crossOrigin);
 
     @JSProperty
-    String getRel();
+    public abstract String getRel();
 
     @JSProperty
-    void setRel(String rel);
+    public abstract void setRel(String rel);
 
     @JSProperty
-    String getMedia();
+    public abstract String getMedia();
 
     @JSProperty
-    void setMedia(String media);
+    public abstract void setMedia(String media);
 
     @JSProperty
-    String getHreflang();
+    public abstract String getHreflang();
 
     @JSProperty
-    void setHreflang(String hreflang);
+    public abstract void setHreflang(String hreflang);
 
     @JSProperty
-    String getType();
+    public abstract String getType();
 
     @JSProperty
-    void setType(String property);
+    public abstract void setType(String property);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMediaElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMediaElement.java
index 542d24651..d5fb130a8 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMediaElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMediaElement.java
@@ -16,6 +16,7 @@
 package org.teavm.jso.dom.html;
 
 import java.util.Date;
+import org.teavm.jso.JSClass;
 import org.teavm.jso.JSProperty;
 import org.teavm.jso.media.AudioTrackList;
 import org.teavm.jso.media.MediaController;
@@ -25,171 +26,168 @@ import org.teavm.jso.media.TextTrackList;
 import org.teavm.jso.media.TimeRanges;
 import org.teavm.jso.media.VideoTrackList;
 
-/**
- *
- * @author Junji Takakura
- */
-public interface HTMLMediaElement extends HTMLElement {
-    int HAVE_NOTHING = 0;
-    int HAVE_METADATA = 1;
-    int HAVE_CURRENT_DATA = 2;
-    int HAVE_FUTURE_DATA = 3;
-    int HAVE_ENOUGH_DATA = 4;
+@JSClass
+public abstract class HTMLMediaElement extends HTMLElement {
+    public static final int HAVE_NOTHING = 0;
+    public static final int HAVE_METADATA = 1;
+    public static final int HAVE_CURRENT_DATA = 2;
+    public static final int HAVE_FUTURE_DATA = 3;
+    public static final int HAVE_ENOUGH_DATA = 4;
 
-    int NETWORK_EMPTY = 0;
-    int NETWORK_IDLE = 1;
-    int NETWORK_LOADING = 2;
-    int NETWORK_NO_SOURCE = 3;
+    public static final int NETWORK_EMPTY = 0;
+    public static final int NETWORK_IDLE = 1;
+    public static final int NETWORK_LOADING = 2;
+    public static final int NETWORK_NO_SOURCE = 3;
 
     @JSProperty
-    MediaError getError();
+    public abstract MediaError getError();
 
     @JSProperty
-    String getSrc();
+    public abstract String getSrc();
 
     @JSProperty
-    void setSrc(String src);
+    public abstract void setSrc(String src);
 
     @JSProperty
-    String getCurrentSrc();
+    public abstract String getCurrentSrc();
 
     @JSProperty
-    String getCrossOrigin();
+    public abstract String getCrossOrigin();
 
     @JSProperty
-    void setCrossOrigin(String crossOrigin);
+    public abstract void setCrossOrigin(String crossOrigin);
 
     @JSProperty
-    int getNetworkState();
+    public abstract int getNetworkState();
 
     @JSProperty
-    String getPreload();
+    public abstract String getPreload();
 
     @JSProperty
-    void setPreload(String preload);
+    public abstract void setPreload(String preload);
 
     @JSProperty
-    TimeRanges getBuffered();
+    public abstract TimeRanges getBuffered();
 
     @JSProperty
-    int getReadyState();
+    public abstract int getReadyState();
 
     @JSProperty
-    boolean isSeeking();
+    public abstract boolean isSeeking();
 
     @JSProperty
-    double getCurrentTime();
+    public abstract double getCurrentTime();
 
     @JSProperty
-    void setCurrentTime(double currentTime);
+    public abstract void setCurrentTime(double currentTime);
 
-    default void addCurrentTime(double delta) {
+    public final void addCurrentTime(double delta) {
         setCurrentTime(getCurrentTime() + delta);
     }
 
     @JSProperty
-    double getDuration();
+    public abstract double getDuration();
 
     @JSProperty
-    Date getStartDate();
+    public abstract Date getStartDate();
 
     @JSProperty
-    boolean isPaused();
+    public abstract boolean isPaused();
 
     @JSProperty
-    double getDefaultPlaybackRate();
+    public abstract double getDefaultPlaybackRate();
 
     @JSProperty
-    void setDefaultPlaybackRate(double defaultPlaybackRate);
+    public abstract void setDefaultPlaybackRate(double defaultPlaybackRate);
 
     @JSProperty
-    double getPlaybackRate();
+    public abstract double getPlaybackRate();
 
     @JSProperty
-    void setPlaybackRate(double playbackRate);
+    public abstract void setPlaybackRate(double playbackRate);
 
-    default void addPlaybackRate(double delta) {
+    public final void addPlaybackRate(double delta) {
         setPlaybackRate(getPlaybackRate() + delta);
     }
 
     @JSProperty
-    TimeRanges getPlayed();
+    public abstract TimeRanges getPlayed();
 
     @JSProperty
-    TimeRanges getSeekable();
+    public abstract TimeRanges getSeekable();
 
     @JSProperty
-    boolean isEnded();
+    public abstract boolean isEnded();
 
     @JSProperty
-    boolean isAutoplay();
+    public abstract boolean isAutoplay();
 
     @JSProperty
-    void setAutoplay(boolean autoplay);
+    public abstract void setAutoplay(boolean autoplay);
 
     @JSProperty
-    boolean isLoop();
+    public abstract boolean isLoop();
 
     @JSProperty
-    void setLoop(boolean loop);
+    public abstract void setLoop(boolean loop);
 
     @JSProperty
-    String getMediaGroup();
+    public abstract String getMediaGroup();
 
     @JSProperty
-    void setMediaGroup(String mediaGroup);
+    public abstract void setMediaGroup(String mediaGroup);
 
     @JSProperty
-    MediaController getController();
+    public abstract MediaController getController();
 
     @JSProperty
-    void setController(MediaController controller);
+    public abstract void setController(MediaController controller);
 
     @JSProperty
-    boolean isControls();
+    public abstract boolean isControls();
 
     @JSProperty
-    void setControls(boolean controls);
+    public abstract void setControls(boolean controls);
 
     @JSProperty
-    float getVolume();
+    public abstract float getVolume();
 
     @JSProperty
-    void setVolume(float volume);
+    public abstract void setVolume(float volume);
 
-    default void addVolume(float delta) {
+    public final void addVolume(float delta) {
         setVolume(getVolume() + delta);
     }
 
     @JSProperty
-    boolean isMuted();
+    public abstract boolean isMuted();
 
     @JSProperty
-    void setMuted(boolean muted);
+    public abstract void setMuted(boolean muted);
 
     @JSProperty
-    boolean isDefaultMuted();
+    public abstract boolean isDefaultMuted();
 
     @JSProperty
-    void setDefaultMuted(boolean defaultMuted);
+    public abstract void setDefaultMuted(boolean defaultMuted);
 
-    AudioTrackList getAudioTracks();
+    public abstract AudioTrackList getAudioTracks();
 
-    VideoTrackList getVideoTracks();
+    public abstract VideoTrackList getVideoTracks();
 
-    TextTrackList getTextTracks();
+    public abstract TextTrackList getTextTracks();
 
-    TextTrack addTextTrack(String kind);
+    public abstract TextTrack addTextTrack(String kind);
 
-    TextTrack addTextTrack(String kind, String label);
+    public abstract TextTrack addTextTrack(String kind, String label);
 
-    TextTrack addTextTrack(String kind, String label, String language);
+    public abstract TextTrack addTextTrack(String kind, String label, String language);
 
-    void play();
+    public abstract void play();
 
-    void pause();
+    public abstract void pause();
 
-    void load();
+    public abstract void load();
 
-    String canPlayType(String type);
+    public abstract String canPlayType(String type);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMetaElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMetaElement.java
index 48cba22ba..6d7a6e314 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMetaElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLMetaElement.java
@@ -17,22 +17,22 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLMetaElement extends HTMLElement {
+public abstract class HTMLMetaElement extends HTMLElement {
     @JSProperty
-    String getName();
+    public abstract String getName();
 
     @JSProperty
-    void setName(String name);
+    public abstract void setName(String name);
 
     @JSProperty
-    String getHttpEquiv();
+    public abstract String getHttpEquiv();
 
     @JSProperty
-    void setHttpEquiv(String httpEquiv);
+    public abstract void setHttpEquiv(String httpEquiv);
 
     @JSProperty
-    String getContent();
+    public abstract String getContent();
 
     @JSProperty
-    void setContent(String content);
+    public abstract void setContent(String content);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLOptionElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLOptionElement.java
index 9142ef02f..854fe7559 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLOptionElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLOptionElement.java
@@ -17,43 +17,43 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLOptionElement extends HTMLElement {
+public abstract class HTMLOptionElement extends HTMLElement {
     @JSProperty
-    boolean isDisabled();
+    public abstract boolean isDisabled();
 
     @JSProperty
-    void setDisabled(boolean disabled);
+    public abstract void setDisabled(boolean disabled);
 
     @JSProperty
-    String getLabel();
+    public abstract String getLabel();
 
     @JSProperty
-    void setLabel(String label);
+    public abstract void setLabel(String label);
 
     @JSProperty
-    boolean isDefaultSelected();
+    public abstract boolean isDefaultSelected();
 
     @JSProperty
-    void setDefaultSelected(boolean defaultSelected);
+    public abstract void setDefaultSelected(boolean defaultSelected);
 
     @JSProperty
-    boolean isSelected();
+    public abstract boolean isSelected();
 
     @JSProperty
-    void setSelected(boolean selected);
+    public abstract void setSelected(boolean selected);
 
     @JSProperty
-    String getValue();
+    public abstract String getValue();
 
     @JSProperty
-    void setValue(String value);
+    public abstract void setValue(String value);
 
     @JSProperty
-    String getText();
+    public abstract String getText();
 
     @JSProperty
-    void setText(String text);
+    public abstract void setText(String text);
 
     @JSProperty
-    int getIndex();
+    public abstract int getIndex();
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLScriptElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLScriptElement.java
index c2c5f2aff..642a79530 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLScriptElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLScriptElement.java
@@ -17,40 +17,40 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLScriptElement extends HTMLElement {
+public abstract class HTMLScriptElement extends HTMLElement {
     @JSProperty
-    String getSrc();
+    public abstract String getSrc();
 
     @JSProperty
-    void setSrc(String value);
+    public abstract void setSrc(String value);
 
     @JSProperty
-    boolean isAsync();
+    public abstract boolean isAsync();
 
     @JSProperty
-    void setAsync(boolean value);
+    public abstract void setAsync(boolean value);
 
     @JSProperty
-    boolean isDefer();
+    public abstract boolean isDefer();
 
     @JSProperty
-    void setDefer(boolean value);
+    public abstract void setDefer(boolean value);
 
     @JSProperty
-    String getType();
+    public abstract String getType();
 
     @JSProperty
-    void setType(String value);
+    public abstract void setType(String value);
 
     @JSProperty
-    String getCharset();
+    public abstract String getCharset();
 
     @JSProperty
-    void setCharset(String value);
+    public abstract void setCharset(String value);
 
     @JSProperty
-    String getText();
+    public abstract String getText();
 
     @JSProperty
-    void setText(String value);
+    public abstract void setText(String value);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSelectElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSelectElement.java
index 5affcec34..7347d90ac 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSelectElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSelectElement.java
@@ -17,47 +17,47 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLSelectElement extends HTMLElement {
+public abstract class HTMLSelectElement extends HTMLElement {
     @JSProperty
-    boolean isDisabled();
+    public abstract boolean isDisabled();
 
     @JSProperty
-    void setDisabled(boolean disabled);
+    public abstract void setDisabled(boolean disabled);
 
     @JSProperty
-    boolean isMultiple();
+    public abstract boolean isMultiple();
 
     @JSProperty
-    void setMultiple(boolean multiple);
+    public abstract void setMultiple(boolean multiple);
 
     @JSProperty
-    HTMLOptionsCollection getOptions();
+    public abstract HTMLOptionsCollection getOptions();
 
     @JSProperty
-    String getName();
+    public abstract String getName();
 
     @JSProperty
-    void setName(String name);
+    public abstract void setName(String name);
 
     @JSProperty
-    int getSize();
+    public abstract int getSize();
 
     @JSProperty
-    void setSize(int size);
+    public abstract void setSize(int size);
 
     @JSProperty
-    int getSelectedIndex();
+    public abstract int getSelectedIndex();
 
     @JSProperty
-    void setSelectedIndex(int selectedIndex);
+    public abstract void setSelectedIndex(int selectedIndex);
 
     @JSProperty
-    String getValue();
+    public abstract String getValue();
 
     @JSProperty
-    void setValue(String value);
+    public abstract void setValue(String value);
 
-    void setCustomValidity(String validationFailure);
+    public abstract void setCustomValidity(String validationFailure);
     
-    boolean reportValidity();
+    public abstract boolean reportValidity();
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSourceElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSourceElement.java
index 0dd74d990..2b7a1d3e0 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSourceElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLSourceElement.java
@@ -17,28 +17,24 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-/**
- *
- * @author Junji Takakura
- */
-public interface HTMLSourceElement extends HTMLElement {
+public abstract class HTMLSourceElement extends HTMLElement {
 
     @JSProperty
-    String getType();
+    public abstract String getType();
 
     @JSProperty
-    void setType(String type);
+    public abstract void setType(String type);
 
     @JSProperty
-    String getSrc();
+    public abstract String getSrc();
 
     @JSProperty
-    void setSrc(String src);
+    public abstract void setSrc(String src);
 
     @JSProperty
-    String getMedia();
+    public abstract String getMedia();
 
     @JSProperty
-    void setMedia(String media);
+    public abstract void setMedia(String media);
 
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTextAreaElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTextAreaElement.java
index b92e4de52..4264486e8 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTextAreaElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTextAreaElement.java
@@ -17,133 +17,133 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLTextAreaElement extends HTMLElement {
+public abstract class HTMLTextAreaElement extends HTMLElement {
     @JSProperty
-    String getAutocomplete();
+    public abstract String getAutocomplete();
 
     @JSProperty
-    void setAutocomplete(String value);
+    public abstract void setAutocomplete(String value);
 
     @JSProperty
-    boolean isAutofocus();
+    public abstract boolean isAutofocus();
 
     @JSProperty
-    void setAutofocus(boolean value);
+    public abstract void setAutofocus(boolean value);
 
     @JSProperty
-    int getCols();
+    public abstract int getCols();
 
     @JSProperty
-    void setCols(int cols);
+    public abstract void setCols(int cols);
 
     @JSProperty
-    String getDirName();
+    public abstract String getDirName();
 
     @JSProperty
-    void setDirName(String value);
+    public abstract void setDirName(String value);
 
     @JSProperty
-    boolean isDisabled();
+    public abstract boolean isDisabled();
 
     @JSProperty
-    void setDisabled(boolean value);
+    public abstract void setDisabled(boolean value);
 
     @JSProperty
-    HTMLFormElement getForm();
+    public abstract HTMLFormElement getForm();
 
     @JSProperty
-    int getMaxLength();
+    public abstract int getMaxLength();
 
     @JSProperty
-    void setMaxLength(int value);
+    public abstract void setMaxLength(int value);
 
     @JSProperty
-    int getMinLength();
+    public abstract int getMinLength();
 
     @JSProperty
-    void setMinLength(int value);
+    public abstract void setMinLength(int value);
 
     @JSProperty
-    String getName();
+    public abstract String getName();
 
     @JSProperty
-    void setName(String value);
+    public abstract void setName(String value);
 
     @JSProperty
-    String getPlaceholder();
+    public abstract String getPlaceholder();
 
     @JSProperty
-    void setPlaceholder(String value);
+    public abstract void setPlaceholder(String value);
 
     @JSProperty
-    boolean isReadOnly();
+    public abstract boolean isReadOnly();
 
     @JSProperty
-    void setReadOnly(boolean value);
+    public abstract void setReadOnly(boolean value);
 
     @JSProperty
-    int getRows();
+    public abstract int getRows();
 
     @JSProperty
-    void setRows(int rows);
+    public abstract void setRows(int rows);
 
     @JSProperty
-    String getWrap();
+    public abstract String getWrap();
 
     @JSProperty
-    void setWrap(String value);
+    public abstract void setWrap(String value);
 
     @JSProperty
-    String getType();
+    public abstract String getType();
 
     @JSProperty
-    String getDefaultValue();
+    public abstract String getDefaultValue();
 
     @JSProperty
-    void setDefaultValue(String value);
+    public abstract void setDefaultValue(String value);
 
     @JSProperty
-    String getValue();
+    public abstract String getValue();
 
     @JSProperty
-    void setValue(String value);
+    public abstract void setValue(String value);
 
     @JSProperty
-    int getTextLength();
+    public abstract int getTextLength();
 
-    void setCustomValidity(String validationFailure);
+    public abstract void setCustomValidity(String validationFailure);
     
-    boolean checkValidity();
+    public abstract boolean checkValidity();
     
-    boolean reportValidity();
+    public abstract boolean reportValidity();
 
-    void select();
+    public abstract void select();
 
     @JSProperty
-    int getSelectionStart();
+    public abstract int getSelectionStart();
 
     @JSProperty
-    void setSelectionStart(int value);
+    public abstract void setSelectionStart(int value);
 
     @JSProperty
-    int getSelectionEnd();
+    public abstract int getSelectionEnd();
 
     @JSProperty
-    void setSelectionEnd(int value);
+    public abstract void setSelectionEnd(int value);
 
     @JSProperty
-    String getSelectionDirection();
+    public abstract String getSelectionDirection();
 
     @JSProperty
-    void setSelectionDirection(String value);
+    public abstract void setSelectionDirection(String value);
 
-    void setRangeText(String replacement);
+    public abstract void setRangeText(String replacement);
 
-    void setRangeText(String replacement, int start, int end, String selectionMode);
+    public abstract void setRangeText(String replacement, int start, int end, String selectionMode);
 
-    void setRangeText(String replacement, int start, int end);
+    public abstract void setRangeText(String replacement, int start, int end);
 
-    void setSelectionRange(int start, int end, String direction);
+    public abstract void setSelectionRange(int start, int end, String direction);
 
-    void setSelectionRange(int start, int end);
+    public abstract void setSelectionRange(int start, int end);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTitleElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTitleElement.java
index 36a253a74..5b53f8a08 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTitleElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLTitleElement.java
@@ -17,10 +17,10 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-public interface HTMLTitleElement extends HTMLElement {
+public abstract class HTMLTitleElement extends HTMLElement {
     @JSProperty
-    String getText();
+    public abstract String getText();
 
     @JSProperty
-    void setText(String text);
+    public abstract void setText(String text);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLVideoElement.java b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLVideoElement.java
index b361ff8f1..7b767f86f 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLVideoElement.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/html/HTMLVideoElement.java
@@ -17,33 +17,29 @@ package org.teavm.jso.dom.html;
 
 import org.teavm.jso.JSProperty;
 
-/**
- *
- * @author Junji Takakura
- */
-public interface HTMLVideoElement extends HTMLMediaElement {
+public abstract class HTMLVideoElement extends HTMLMediaElement {
 
     @JSProperty
-    int getWidth();
+    public abstract int getWidth();
 
     @JSProperty
-    int getHeight();
+    public abstract int getHeight();
 
     @JSProperty
-    void setWidth(int width);
+    public abstract void setWidth(int width);
 
     @JSProperty
-    void setHeight(int height);
+    public abstract void setHeight(int height);
 
     @JSProperty
-    int getVideoWidth();
+    public abstract int getVideoWidth();
 
     @JSProperty
-    int getVideoHeight();
+    public abstract int getVideoHeight();
 
     @JSProperty
-    String getPoster();
+    public abstract String getPoster();
 
     @JSProperty
-    void setPoster(String poster);
+    public abstract void setPoster(String poster);
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/xml/DOMParser.java b/jso/apis/src/main/java/org/teavm/jso/dom/xml/DOMParser.java
index c75bfe3a5..1d50e21a0 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/xml/DOMParser.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/xml/DOMParser.java
@@ -16,6 +16,7 @@
 package org.teavm.jso.dom.xml;
 
 import org.teavm.jso.JSBody;
+import org.teavm.jso.JSClass;
 import org.teavm.jso.JSObject;
 import org.teavm.jso.dom.html.HTMLDocument;
 
@@ -23,9 +24,13 @@ import org.teavm.jso.dom.html.HTMLDocument;
  * The DOMParser interface provides the ability to parse XML or HTML source code from
  * a string into a DOM {@link Document}.
  */
-public abstract class DOMParser implements JSObject {
+@JSClass
+public class DOMParser implements JSObject {
+    public DOMParser() {
+    }
 
     @JSBody(script = "return new DOMParser();")
+    @Deprecated
     public static native DOMParser create();
     
     /**
@@ -51,6 +56,6 @@ public abstract class DOMParser implements JSObject {
      *        application/xml, application/xhtml+xml, image/svg+xml
      * @return Newly created {@link Document} or {@link HTMLDocument}
      */
-    public abstract Document parseFromString(String s, String mimeType);
+    public native Document parseFromString(String s, String mimeType);
     
 }
diff --git a/jso/apis/src/main/java/org/teavm/jso/dom/xml/XMLSerializer.java b/jso/apis/src/main/java/org/teavm/jso/dom/xml/XMLSerializer.java
index 2e11b2021..16d197609 100644
--- a/jso/apis/src/main/java/org/teavm/jso/dom/xml/XMLSerializer.java
+++ b/jso/apis/src/main/java/org/teavm/jso/dom/xml/XMLSerializer.java
@@ -16,32 +16,21 @@
 package org.teavm.jso.dom.xml;
 
 import org.teavm.jso.JSBody;
+import org.teavm.jso.JSClass;
 import org.teavm.jso.JSObject;
 
 /**
  * The XMLSerializer interface provides the ability to construct an XML string
  * representing a DOM tree.
  */
-public abstract class XMLSerializer implements JSObject {
+@JSClass
+public class XMLSerializer implements JSObject {
+    public XMLSerializer() {
+    }
 
     @JSBody(script = "return new XMLSerializer();")
+    @Deprecated
     public static native XMLSerializer create();
-    
-    /**
-     * Constructs a string representing the specified DOM tree in XML form.
-     *
-     * @param rootNode The Node to use as the root of the DOM tree or subtree for
-     *        which to construct an XML representation. The root node itself must be
-     *        either a {@link Node} or {@link Attr} object.
-     * @return A DOMString containing the XML representation of the specified DOM
-     *         tree.
-     * @throws TypeError The specified rootNode is not a compatible node type. The
-     *         root node must be either Node or Attr.
-     * @throws InvalidStateError The tree could not be successfully serialized,
-     *         probably due to issues with the content's compatibility with XML
-     *         serialization.
-     * @throws SyntaxError A serialization of HTML was requested but could not
-     *         succeed due to the content not being well-formed.
-     */
-    public abstract String serializeToString(Node rootNode);
+
+    public native String serializeToString(Node rootNode);
 }