His biggest point is “do not optimize prematurely”. This is a sentiment I’ve heard a few times. Fred Brooks emphasizes it in Mythical Man Month, and Eric Raymond harps on it a bit in Art of Unix Programming.

Another point he makes is how using “weird language syntax” like double bitwise not is sometimes faster than their functional equivalents like parseInt.

And one surprising revelation (for me anyway) is that unrolled loops can sometimes be faster.

Overall, a great presentation, well worth your time if you work with javascript a lot.

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After scouring the web for clues to help me get rid of this warning without changing settings on the browser, I found out that the only way to avoid these warnings was through a pseudo-threading pattern using setTimeout¹².

One of the patterns I came up with to process a sequence of commands (such as adding records to a store) one at a time while still allowing the browser time to refresh and process other commands:

var chainedTasks = [
   function() {
      console.log('first set of tasks');
   },
   function() {
      console.log('second set of tasks');
   },
   function() {
      console.log('third set of tasks');
   }
];

var currentTaskNum = 0;
var isExecuting = false;
var emptask = {var emptask = {
	scope: this,
	interval: 100,
	run: function(){
		if(currentTaskNum > chainedTasks.length) {
			Ext.TaskMgr.stop(emptask);
		}

		if (!threadIsRunning) {
			threadIsRunning = true;
			if (typeof chainedTasks[currentTaskNum] === 'function') {
				chainedTasks[currentTaskNum](currentTaskNum);
			}
			currentTaskNum++;
			threadIsRunning = false;
		}
	}
};
Ext.TaskMgr.start(emptask);

1. http://www.dojotoolkit.org/forum/support/general-support/need-suggestions-how-manage-firefox-warning-unresponsive-script
2. http://dev.opera.com/articles/view/efficient-javascript/?page=all

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Enter Ext.TaskMgr, a helpful ExtJS object that is essentially a glorified setTimeout implementation that allows us to run tasks that don’t block execution. This means we can set our more expensive blocks of code to run later but return control back to the user in the meantime. It’s not true multi-threading, but it does allow us to make the user interface a lot more responsive and in an age when users think 5 seconds is an eternity, perception is everything.

1. In other words, it sucks pretty bad.