mocha browser runner is 10-100x slower than jasmine on equivalent suites

lib/reporters/html.js

@@ -120,8 +120,6 @@ function HTML(runner, root) {
   });
 
   runner.on('test end', function(test){
-    window.scrollTo(0, document.body.scrollHeight);
-
     // TODO: add to stats
     var percent = stats.tests / this.total * 100 | 0;
     if (progress) progress.update(percent).draw(ctx);

lib/runner.js

@@ -8,9 +8,7 @@ var EventEmitter = require('events').EventEmitter
   , Test = require('./test')
   , utils = require('./utils')
   , filter = utils.filter
-  , keys = utils.keys
-  , noop = function(){}
-  , immediately = global.setImmediate || process.nextTick;
+  , keys = utils.keys;
 
 /**
  * Non-enumerable globals.
@@ -62,6 +60,14 @@ function Runner(suite) {
   this.globals(this.globalProps().concat(['errno']));
 }
 
+/**
+ * Wrapper for setImmediate, process.nextTick, or browser polyfill.
+ *
+ * @param {Function} fn
+ * @api private
+ */
+Runner.immediately = global.setImmediate || process.nextTick;
+
 /**
  * Inherit from `EventEmitter.prototype`.
  */
@@ -243,7 +249,7 @@ Runner.prototype.hook = function(name, fn){
     });
   }
 
-  immediately(function(){
+  Runner.immediately(function(){
     next(0);
   });
 };

lib/utils.js

@@ -107,7 +107,7 @@ exports.filter = function(arr, fn){
  * @api private
  */
 
-exports.keys = function(obj) {
+exports.keys = Object.keys || function(obj) {
   var keys = []
     , has = Object.prototype.hasOwnProperty // for `window` on <=IE8
 

support/tail.js

@@ -12,34 +12,6 @@ process.exit = function(status){};
 process.stdout = {};
 global = window;
 
-/**
- * next tick implementation.
- */
-
-process.nextTick = (function(){
-  // postMessage behaves badly on IE8
-  if (window.ActiveXObject || !window.postMessage) {
-    return function(fn){ fn() };
-  }
-
-  // based on setZeroTimeout by David Baron
-  // - http://dbaron.org/log/20100309-faster-timeouts
-  var timeouts = []
-    , name = 'mocha-zero-timeout'
-
-  window.addEventListener('message', function(e){
-    if (e.source == window && e.data == name) {
-      if (e.stopPropagation) e.stopPropagation();
-      if (timeouts.length) timeouts.shift()();
-    }
-  }, true);
-
-  return function(fn){
-    timeouts.push(fn);
-    window.postMessage(name, '*');
-  }
-})();
-
 /**
  * Remove uncaughtException listener.
  */
@@ -72,6 +44,31 @@ process.on = function(e, fn){
   var Mocha = window.Mocha = require('mocha'),
       mocha = window.mocha = new Mocha({ reporter: 'html' });
 
+  var immediateQueue = []
+    , immediateTimeout;
+
+  function timeslice() {
+    var immediateStart = new Date().getTime();
+    while (immediateQueue.length && (new Date().getTime() - immediateStart) < 100) {
+      immediateQueue.shift()();
+    }
+    if (immediateQueue.length) {
+      immediateTimeout = setTimeout(timeslice, 0);
+    } else {
+      immediateTimeout = null;
+    }
+  }
+
+  /**
+   * High-performance override of Runner.immediately.
+   */
+  Mocha.Runner.immediately = function(callback) {
+    immediateQueue.push(callback);
+    if (!immediateTimeout) {
+      immediateTimeout = setTimeout(timeslice, 0);
+    }
+  };
+
   /**
    * Override ui to ensure that the ui functions are initialized.
    * Normally this would happen in Mocha.prototype.loadFiles.