Change XMLHttpRequest error handling

index.js

@@ -61,14 +61,25 @@ function json(url, obj, headers, fn){
   if (3 == arguments.length) fn = headers, headers = {};
 
   var req = new XMLHttpRequest;
-  req.onerror = fn;
-  req.onreadystatechange = done;
+  req.onerror = error;
+  req.onload = done;
   req.open('POST', url, true);
   for (var k in headers) req.setRequestHeader(k, headers[k]);
   req.send(JSON.stringify(obj));
 
   function done(){
-    if (4 == req.readyState) return fn(null, req);
+    // sometimes IE returns 1223 when it should be 204
+    // see http://stackoverflow.com/questions/10046972/msie-returns-status-code-of-1223-for-ajax-request
+    if (/^(20\d|1223)$/.test(req.status)) {
+      return fn(null, req)
+    }
+    fn(new Error("Request wasn't successful"), req);
+  }
+
+  function error(event){
+    var err = new Error("A network error ocurred");
+    err.event = event;
+    fn(err);
   }
 }
 

test/test.js

@@ -20,6 +20,29 @@ describe('send-json', function(){
         done();
       });
     })
+
+    it('should invoke the callback with an error when connection is refused', function(done){
+      if ('xhr' != send.type) return done();
+      var url = protocol() + '//localhost:4567/data';
+      var headers = { 'Content-Type': 'application/json' };
+      send.json(url, [1, 2, 3], headers, function(err, req){
+        assert(err);
+        assert(typeof err.event === "object");
+        done();
+      });
+    })
+
+    it('should invoke the callback with an error when the request does not succeed', function(done){
+      if ('xhr' != send.type) return done();
+      var url = protocol() + '//localhost:3001/not-found';
+      var headers = { 'Content-Type': 'application/json' };
+      send.json(url, [1, 2, 3], headers, function(err, req){
+        assert(err);
+        assert(typeof req === "object");
+        assert(req.status === 404);
+        done();
+      });
+    })
   })
 
   describe('#base64', function(){