Make fetch.blob() work

js/fetch.ts

@@ -20,6 +20,7 @@ import {
   FormData
 } from "./dom_types";
 import { TextDecoder } from "./text_encoding";
+import { DenoBlob } from "./blob";
 
 interface Header {
   name: string;
@@ -134,8 +135,10 @@ class FetchResponse implements Response {
   }
 
   async blob(): Promise<Blob> {
-    notImplemented();
-    return {} as Blob;
+    const arrayBuffer = await this.arrayBuffer();
+    return new DenoBlob([arrayBuffer], {
+      type: this.headers.get("content-type") || ""
+    });
   }
 
   async formData(): Promise<FormData> {

js/fetch_test.ts

@@ -35,3 +35,11 @@ test(async function headersAppend() {
   }
   assert(err instanceof TypeError);
 });
+
+testPerm({ net: true }, async function fetchBlob() {
+  const response = await fetch("http://localhost:4545/package.json");
+  const headers = response.headers;
+  const blob = await response.blob();
+  assertEqual(blob.type, headers.get("Content-Type"));
+  assertEqual(blob.size, Number(headers.get("Content-Length")));
+});

js/util.ts

@@ -9,7 +9,7 @@ export function setLogDebug(debug: boolean): void {
 }
 
 /**
- * Debug logging for deno. 
+ * Debug logging for deno.
  * Enable with the `--log-debug` or `-D` command line flag.
  * @internal
  */