2 files changed, 28 insertions, 2 deletions
diff --git a/js/fetch.ts b/js/fetch.ts
index 3559f3db8..25db32d1d 100644
--- a/js/fetch.ts
+++ b/js/fetch.ts
@@ -128,6 +128,7 @@ class FetchResponse implements domTypes.Response {
   readonly trailer: Promise<domTypes.Headers>;
   //private bodyChunks: Uint8Array[] = [];
   private first = true;
+  private bodyData: ArrayBuffer;
   private bodyWaiter: Resolvable<ArrayBuffer>;
 
   constructor(
@@ -138,6 +139,7 @@ class FetchResponse implements domTypes.Response {
     this.bodyWaiter = createResolvable();
     this.trailer = createResolvable();
     this.headers = new DenoHeaders(headersList);
+    this.bodyData = body_;
     setTimeout(() => {
       this.bodyWaiter.resolve(body_);
     }, 0);
@@ -175,8 +177,19 @@ class FetchResponse implements domTypes.Response {
   }
 
   clone(): domTypes.Response {
-    notImplemented();
-    return {} as domTypes.Response;
+    if (this.bodyUsed) {
+      throw new TypeError(
+        "Failed to execute 'clone' on 'Response': Response body is already used"
+      );
+    }
+
+    const iterators = this.headers.entries();
+    const headersList: Array<[string, string]> = [];
+    for (const header of iterators) {
+      headersList.push(header);
+    }
+
+    return new FetchResponse(this.status, this.bodyData.slice(0), headersList);
   }
 
   onHeader?: (res: FetchResponse) => void;
diff --git a/js/fetch_test.ts b/js/fetch_test.ts
index 2ef58f273..2f73544aa 100644
--- a/js/fetch_test.ts
+++ b/js/fetch_test.ts
@@ -44,6 +44,19 @@ testPerm({ net: true }, async function fetchBlob() {
   assertEqual(blob.size, Number(headers.get("Content-Length")));
 });
 
+testPerm({ net: true }, async function responseClone() {
+  const response = await fetch("http://localhost:4545/package.json");
+  const response1 = response.clone();
+  assert(response !== response1);
+  assertEqual(response.status, response1.status);
+  assertEqual(response.statusText, response1.statusText);
+  const ab = await response.arrayBuffer();
+  const ab1 = await response1.arrayBuffer();
+  for (let i = 0; i < ab.byteLength; i++) {
+    assertEqual(ab[i], ab1[i]);
+  }
+});
+
 // Logic heavily copied from web-platform-tests, make
 // sure pass mostly header basic test
 /* tslint:disable-next-line:max-line-length */