Window: implement queueMicrotask()

duonglaiquang · rbri · commit c4e31e41d2f7 · 2026-03-12T13:24:37.000+01:00
diff --git a/src/main/java/org/htmlunit/javascript/host/Window.java b/src/main/java/org/htmlunit/javascript/host/Window.java
@@ -139,6 +139,7 @@
  * @author Colin Alworth
  * @author Atsushi Nakagawa
  * @author Sven Strickroth
+ * @author Lai Quang Duong
  *
  * @see <a href="http://msdn.microsoft.com/en-us/library/ms535873.aspx">MSDN documentation</a>
  */
@@ -492,6 +493,24 @@ public static Object setTimeout(final Context context, final Scriptable scope,
         return WindowOrWorkerGlobalScopeMixin.setTimeout(context, thisObj, args, function);
     }
 
+    /**
+     * Queues a microtask to be executed.
+     *
+     * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/queueMicrotask">
+     *     MDN web docs</a>
+     * @param context the JavaScript context
+     * @param scope the scope
+     * @param thisObj the scriptable
+     * @param args the arguments passed into the method
+     * @param function the function
+     * @return undefined
+     */
+    @JsxFunction
+    public static Object queueMicrotask(final Context context, final Scriptable scope,
+            final Scriptable thisObj, final Object[] args, final Function function) {
+        return WindowOrWorkerGlobalScopeMixin.queueMicrotask(thisObj, args);
+    }
+
     /**
      * Sets a chunk of JavaScript to be invoked each time a specified number of milliseconds has elapsed.
      *
diff --git a/src/main/java/org/htmlunit/javascript/host/WindowOrWorkerGlobalScopeMixin.java b/src/main/java/org/htmlunit/javascript/host/WindowOrWorkerGlobalScopeMixin.java
@@ -24,6 +24,7 @@
 import org.htmlunit.corejs.javascript.Function;
 import org.htmlunit.corejs.javascript.FunctionObject;
 import org.htmlunit.corejs.javascript.Scriptable;
+import org.htmlunit.corejs.javascript.ScriptableObject;
 import org.htmlunit.javascript.HtmlUnitScriptable;
 import org.htmlunit.javascript.JavaScriptEngine;
 import org.htmlunit.javascript.background.BackgroundJavaScriptFactory;
@@ -36,6 +37,7 @@
  *
  * @author Ronald Brill
  * @author Rural Hunter
+ * @author Lai Quang Duong
  */
 public final class WindowOrWorkerGlobalScopeMixin {
 
@@ -151,6 +153,38 @@ public static Object setInterval(final Context context, final Scriptable thisObj
         return setTimeoutIntervalImpl((Window) thisObj, args[0], timeout, false, params);
     }
 
+    /**
+     * Queues a microtask to be executed.
+     *
+     * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/queueMicrotask">
+     *     MDN web docs</a>
+     * @param thisObj the scriptable
+     * @param args the arguments passed into the method
+     * @return undefined
+     */
+    public static Object queueMicrotask(final Scriptable thisObj, final Object[] args) {
+        if (args.length < 1) {
+            throw JavaScriptEngine.typeError("At least 1 argument required");
+        }
+        if (!(args[0] instanceof Function)) {
+            throw JavaScriptEngine.typeError("Argument 1 is not callable");
+        }
+
+        final Function callback = (Function) args[0];
+        final Scriptable scope = ScriptableObject.getTopLevelScope(thisObj);
+        final Context cx = Context.getCurrentContext();
+        cx.enqueueMicrotask(() -> {
+            try {
+                callback.call(cx, scope, thisObj, JavaScriptEngine.EMPTY_ARGS);
+            }
+            catch (final Exception e) {
+                // uncaught exception in a microtask must not prevent remaining microtasks from running.
+            }
+        });
+
+        return JavaScriptEngine.UNDEFINED;
+    }
+
     private static int setTimeoutIntervalImpl(final Window window, final Object code,
             int timeout, final boolean isTimeout, final Object[] params) {
         if (timeout < MIN_TIMER_DELAY) {
diff --git a/src/test/java/org/htmlunit/javascript/host/Window2Test.java b/src/test/java/org/htmlunit/javascript/host/Window2Test.java
@@ -19,6 +19,7 @@
 import java.io.OutputStreamWriter;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
+import java.time.Duration;
 
 import org.apache.commons.io.FileUtils;
 import org.htmlunit.CookieManager4Test;
@@ -43,6 +44,7 @@
  * @author Carsten Steul
  * @author Colin Alworth
  * @author Christoph Burgmer
+ * @author Lai Quang Duong
  */
 public class Window2Test extends WebDriverTestCase {
 
@@ -3496,4 +3498,58 @@ public void overwriteProperty_top() throws Exception {
         final WebDriver driver = loadPage2(html);
         verifySessionStorage2(driver, getExpectedAlerts());
     }
+
+    /**
+     * @throws Exception if the test fails
+     */
+    @Test
+    @Alerts("TypeError")
+    public void queueMicrotaskNoArgs() throws Exception {
+        final String html = DOCTYPE_HTML
+            + "<html><head><script>\n"
+            + LOG_TITLE_FUNCTION
+            + "  try { queueMicrotask(); } catch(e) { logEx(e); }\n"
+            + "</script></head></html>";
+
+        loadPageVerifyTitle2(html);
+    }
+
+    /**
+     * @throws Exception if the test fails
+     */
+    @Test
+    @Alerts("TypeError")
+    public void queueMicrotaskNonFunction() throws Exception {
+        final String html = DOCTYPE_HTML
+            + "<html><head><script>\n"
+            + LOG_TITLE_FUNCTION
+            + "  try { queueMicrotask('str'); } catch(e) { logEx(e); }\n"
+            + "</script></head></html>";
+
+        loadPageVerifyTitle2(html);
+    }
+
+    /**
+     * @throws Exception if the test fails
+     */
+    @Test
+    @Alerts("1-sync, 2-microtask, 3-microtask, 4-nested-microtask, 5-timeout")
+    public void queueMicrotaskExecutionOrder() throws Exception {
+        final String html = DOCTYPE_HTML
+            + "<html><head><script>\n"
+            + LOG_TITLE_FUNCTION
+            + "  var r = [];\n"
+            + "  queueMicrotask(function() { r.push('2-microtask'); });\n"
+            + "  setTimeout(function() { r.push('5-timeout'); }, 0);\n"
+            + "  queueMicrotask(function() {\n"
+            + "    r.push('3-microtask');\n"
+            + "    queueMicrotask(function() { r.push('4-nested-microtask'); });\n"
+            + "  });\n"
+            + "  r.push('1-sync');\n"
+            + "  setTimeout(function() { log(r.join(', ')); }, 200);\n"
+            + "</script></head></html>";
+
+        final WebDriver driver = loadPage2(html);
+        verifyTitle2(Duration.ofSeconds(1), driver, getExpectedAlerts());
+    }
 }
