jQuery 开发者应该注意的9个错误
2024-05-06 14:22:06
供稿：网友
jQuery is so easy to use that sometimes we just forget that it's not CSS. While using CSS, we don't have to give much thought to performance, because it's so fast that it's not worth the effort to optimize it. But when it comes to the real world, jQuery can drive developers crazy with performance issues. Sometimes you lose precious milliseconds without even noticing it. Also, it's so easy to forget about some functions and we keep using the old (and not-so-good) ones.
Let's take a look at a few of the most-common-and-easiest-to-fix mistakes while using jQuery in your projects.
1. You aren't using the latest jQuery version
Each version update means higher performance and several bug fixes. The current stable release is 1.7.2, and I'm pretty sure you know about plenty of sites developed using 1.6 and below. Ok, ok, you can't just update every old site for every jQuery update (unless your client is paying you to do so) but you should at least start using it for your new projects. So, forget about this local copy and just grab the latest release every time you start a new project.
2. You aren't using a CDN-hosted copy of jQuery
How many unique visitors you`ve got last month? I bet the number is still under 1 billion, right?
So you'd better use Google's copy of jQuery instead of yours. If your user still has the cached file of Google's website (or from many other sites that uses its CDN) his browser will just get the cached version, improving a lot your website's performance. You can use it by copying & pasting this HTML:
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
3. You aren't using a fallback for CDN version
I know I said Google is awesome and stuff, but they can fail. So, every time you rely upon external sources, make sure you have a local fallback. I've seen this snippet in the HTML5 boilerplate source code and just found it amazing. You should use it too:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/libs/jquery-1.7.2.min.js"><//script>')</script>
4. You aren't chaining stuff
While doing common operations, you don't need to call the element every time you want to manipulate it. If you're doing several manipulations in a row, use chaining, so jQuery won't need to get the element twice.
Instead of this:
$(“#mydiv”).hide();
$(“#mydiv”).css(“padding-left”, “50px”);
Use this:
$(“#mydiv”).hide().css(“padding-left”, “50px”);
5. You aren't caching stuff
This is one of the most important performance tips. If you'll call an element at least twice, you should cache it. Caching is just saving the jQuery selector in a variable, so when you need to call it again you'll just reference the variable and jQuery won't need to search the whole DOM tree again to find your element.
