Support abort API

fetch.js

@@ -385,6 +385,7 @@
     this.statusText = 'statusText' in options ? options.statusText : 'OK'
     this.headers = new Headers(options.headers)
     this.url = options.url || ''
+    this.signal = options.signal
     this._initBody(bodyInit)
   }
 
@@ -424,6 +425,10 @@
       var request = new Request(input, init)
       var xhr = new XMLHttpRequest()
 
+      if (request.signal && request.signal.aborted) {
+        return reject(new DOMException('Aborted', 'AbortError'));
+      }
+
       xhr.onload = function() {
         var options = {
           status: xhr.status,
@@ -443,6 +448,11 @@
         reject(new TypeError('Network request failed'))
       }
 
+      xhr.onabort = function() {
+        reject(new DOMException('Aborted', 'AbortError'))
+        request.signal.removeEventListener('abort', xhr.abort)
+      }
+
       xhr.open(request.method, request.url, true)
 
       if (request.credentials === 'include') {
@@ -459,6 +469,10 @@
         xhr.setRequestHeader(name, value)
       })
 
+      if (request.signal && request.signal.addEventListener) {
+        request.signal.addEventListener('abort', xhr.abort)
+      }
+
       xhr.send(typeof request._bodyInit === 'undefined' ? null : request._bodyInit)
     })
   }