Merge pull request #647 from share/next-tick

⚡️ Remove artificial 4ms `nextTick()` delay when running in a browser

Author: alecgibson

.mocharc.yml

@@ -2,3 +2,5 @@ reporter: spec
 check-leaks: true
 recursive: true
 file: test/setup.js
+globals:
+- MessageChannel # Set/unset to test nextTick()

lib/util.js

@@ -95,9 +95,20 @@ exports.nextTick = function(callback) {
     args[i - 1] = arguments[i];
   }
 
-  setTimeout(function() {
+  if (typeof MessageChannel === 'undefined') {
+    return setTimeout(triggerCallback);
+  }
+
+  var channel = new MessageChannel();
+  channel.port1.onmessage = function() {
+    triggerCallback();
+    channel.port1.close();
+  };
+  channel.port2.postMessage('');
+
+  function triggerCallback() {
     callback.apply(null, args);
-  });
+  }
 };
 
 exports.clone = function(obj) {

test/util-test.js

@@ -45,6 +45,39 @@ describe('util', function() {
         });
         expect(called).to.be.false;
       });
+
+      describe('without MessageChannel', function() {
+        var _MessageChannel;
+
+        before(function() {
+          _MessageChannel = global.MessageChannel;
+          delete global.MessageChannel;
+        });
+
+        after(function() {
+          global.MessageChannel = _MessageChannel;
+        });
+
+        it('uses a different ponyfill', function(done) {
+          expect(process.nextTick).to.be.undefined;
+
+          util.nextTick(function(arg1, arg2, arg3) {
+            expect(arg1).to.equal('foo');
+            expect(arg2).to.equal(123);
+            expect(arg3).to.be.undefined;
+            done();
+          }, 'foo', 123);
+        });
+
+        it('calls asynchronously', function(done) {
+          var called = false;
+          util.nextTick(function() {
+            called = true;
+            done();
+          });
+          expect(called).to.be.false;
+        });
+      });
     });
   });
 });