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window.$my =
{};
function do_something()
{}
The previous example can also be accomplished like this:
var $active_light = $('#traffic_light input.on');$active_light.bind('click', function(){})
.css('border', '3px dashed yellow')
.css('background-color', 'orange')
.fadeIn('slow'); This allows us to write less co
jQuery allows us to run additional selector operations on a wrapped set. This reduces performance overhead on subsequent selections since we already grabbed and stored the parent object in a local variable.
<div id="content">
<form method="post" action="">
<h2>Traffic Light</h2>
<ul id="traffic_light">
<li><input type="radio" class="on" name="light" value="red" /> Red</li>
<li><input type="radio" class="off" name="light" value="yellow" /> Yellow</li>
<li><input type="radio" class="off" name="light" value="green" /> Green</li>
</ul>
<input class="button" id="traffic_button" type="submit" value="Go" />
</form>
</div>
For example, we can leverage sub-queries to grab the active and inactive lights and cache them for later manipulation.
var $traffic_light = $('#traffic_light'),
$active_light = $traffic_light.find('input.on'),
$inactive_lights = $traffic_light.find('input.off'); Tip: You can declare multiple local variables by separating them with commas – save those bytes!
The basic idea here is to create exactly what you need in memory, and then update the DOM. This is not a jQuery best practice, but a must for efficient JavaS
var top_100_list = [...], // assume this has 100 unique strings
$mylist = $('#mylist'); // jQuery selects our <ul> element
for (var i=0, l=top_100_list.length; i<l; i++)
{}
Instead, we want to create the entire set of elements in a string before inserting into the DOM:
var top_100_list = [...], // assume this has 100 unique strings
$mylist = $('#mylist'), // jQuery selects our <ul> element
top_100_li = ""; // This will store our list items
for (var i=0, l=top_100_list.length; i<l; i++)
{}
$mylist.html(top_100_li);
Even faster, we should always wrap many elements in a single parent node before insertion:
var top_100_list = [...], // assume this has 100 unique strings
$mylist = $('#mylist'), // jQuery selects our <ul> element
top_100_ul = '<ul id="#mylist">'; // This will store our entire unordered list
for (var i=0, l=top_100_list.length; i<l; i++)
{}
top_100_ul += '</ul>'; // Close our unordered list
$mylist.replaceWith(top_100_ul);
If you do the above and are still concerned about performance:
Unless told otherwise, every event (e.g. click, mouseover, etc.) in JavaS
$('#myList li).bind('click', function(){}); Instead, we should listen for the click event at the parent level:
$('#myList).bind('click', function(e){}
}); The parent node acts as a dispatcher and can then do work based on what target element triggered the event. If you find yourself binding on
Although jQuery fails nicely if it does not find any matching elements, it still takes time to look for them. If you have on
<script type="text/javascript>
mylib.article.init();
</script>
</body>
If your page template includes any variety of modules that may or may not be on the page, or for visual reasons you need them to initialize sooner, you could place the initialization function immediately after the module.
<ul id="traffic_light">
<li><input type="radio" class="on" name="light" value="red" /> Red</li>
<li><input type="radio" class="off" name="light" value="yellow" /> Yellow</li>
<li><input type="radio" class="off" name="light" value="green" /> Green</li>
</ul>
<script type="text/javascript>
mylib.traffic_light.init();
</script>
Your Global JS library would look something like this:
var mylib =
{}
},
traffic_light :
{}
}
}
There is a temptation among jQuery developers to hook everything into the
$(window).load(function(){}); Superfluous functionality such as drag and drop, binding visual effects and animations, pre-fetching hidden images, etc., are all good candidates for this technique.
Okay, this isn’t jQuery related, but I had to include it. There is a tendency to make JavaS
Print out this jQuery 1.3 cheat sheet, and make it a goal to eventually understand what each function does. If you find yourself repeating yourself repeating, there is probably an easier (and more efficient) way.