1 files changed, 77 insertions, 0 deletions
diff --git a/cli/rt/03_dom_iterable.js b/cli/rt/03_dom_iterable.js
new file mode 100644
index 000000000..cd190b9cd
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+++ b/cli/rt/03_dom_iterable.js
@@ -0,0 +1,77 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+((window) => {
+  const { requiredArguments } = window.__bootstrap.webUtil;
+  const { exposeForTest } = window.__bootstrap.internals;
+
+  function DomIterableMixin(
+    Base,
+    dataSymbol,
+  ) {
+    // we have to cast `this` as `any` because there is no way to describe the
+    // Base class in a way where the Symbol `dataSymbol` is defined.  So the
+    // runtime code works, but we do lose a little bit of type safety.
+
+    // Additionally, we have to not use .keys() nor .values() since the internal
+    // slot differs in type - some have a Map, which yields [K, V] in
+    // Symbol.iterator, and some have an Array, which yields V, in this case
+    // [K, V] too as they are arrays of tuples.
+
+    const DomIterable = class extends Base {
+      *entries() {
+        for (const entry of this[dataSymbol]) {
+          yield entry;
+        }
+      }
+
+      *keys() {
+        for (const [key] of this[dataSymbol]) {
+          yield key;
+        }
+      }
+
+      *values() {
+        for (const [, value] of this[dataSymbol]) {
+          yield value;
+        }
+      }
+
+      forEach(
+        callbackfn,
+        thisArg,
+      ) {
+        requiredArguments(
+          `${this.constructor.name}.forEach`,
+          arguments.length,
+          1,
+        );
+        callbackfn = callbackfn.bind(
+          thisArg == null ? globalThis : Object(thisArg),
+        );
+        for (const [key, value] of this[dataSymbol]) {
+          callbackfn(value, key, this);
+        }
+      }
+
+      *[Symbol.iterator]() {
+        for (const entry of this[dataSymbol]) {
+          yield entry;
+        }
+      }
+    };
+
+    // we want the Base class name to be the name of the class.
+    Object.defineProperty(DomIterable, "name", {
+      value: Base.name,
+      configurable: true,
+    });
+
+    return DomIterable;
+  }
+
+  exposeForTest("DomIterableMixin", DomIterableMixin);
+
+  window.__bootstrap.domIterable = {
+    DomIterableMixin,
+  };
+})(this);