Brian Grinstead

Sometimes, I want to have a JavaScript event that doesn’t fire until the native event stops firing for a short timeout. I’ve needed to use that pattern in almost every project I have worked on.

For example, you want to use JavaScript to resize an iframe to 100% height when the window resizes. The resize() event can fire dozens of times, and calculating and setting the new height can slow down your page. I used to implement it like this (notice the extra global variable and indentation with the anonymous function):

var timeout;
function doResize(e) {
   clearTimeout(timeout);
   timeout = setTimeout(function() {
      // run some code
   }, 200);
}
$(function() {
   $(window).bind("resize",doResize);
});

I wrote a plugin to make this pattern easier, it is called “bindWithDelay”. The source code is online, as is a mini project page with a demo.

This is what the same code looks like with the plugin:

function doResize(e) {
      // run some code
}
$(function() {
   $(window).bindWithDelay("resize", doResize, 200);
});

Or: Binding Events Inside of a Loop with jQuery

I wrote an article over on the LANIT Development Blog about saving the state of a variable inside a closure that is not executed immediately. For example, functions passed into event binding or setTimeout(). Here is a quick rundown of the problem and the solution (using the jQuery library).

The Problem

$(function() {
	$("body").append("<ul id='container'></ul>");
 
	for (var i = 0; i < 5; i++)
	{
		var $item = $("<li />").text("Item " + i);
		$("#container").append($item);
 
		$item.click(function() {
			alert("You clicked number " + i);  // always "You clicked number 5"
		});
	}
});

The Solution

$(function() {
	$("body").append("<ul id='container'></ul>");
 
	for (var i = 0; i < 5; i++)
	{
		var $item = $("<li />").text("Item " + i);
		$("#container").append($item);
 
		(function() { // Closure here here instead of "bindItem()"
			var ind = i;
			$item.click(function() {
				alert("You clicked number " + ind); // Works as expected
			});
		})(); // Execute immediately
	}
});

The solution uses an immediately executing function to create a new scope and declare a variable “ind” that is reserved a new space in memory instead of simply referencing “i”. Check out the full article for more details.