为什么要将JavaScript放在页面的页脚中？ [英] Why put JavaScript in the footer of a page?

问题描述

所以我最近从ThemeForest购买并下载了一个模板。我在本地服务器上设置了模板。我使用codeigniter生成了具有下拉菜单的导航。我已经正确编码了菜单中的所有内容。我只生成了头文件并进行了测试，发现下拉菜单不起作用。我花了大约两个小时试图弄清楚我的代码出了什么问题。然后，我终于意识到，JavaScript文件已包含在模板的页脚中，这是我还没有生成的。

所以我的问题是......为什么会有人把JavaScript文件放在HTML页面的页脚中？我认为JS只应该位于文件头部。对吗？

解决方案

有几种不同的方法可以将脚本文件加载到网页中。

但是在页面底部加载脚本具有以下优点。

1. 不会阻止任何DOM内容
   
2. 所有DOM元素都可用于正在加载的脚本。


3. 如果您使用的是第三方库，如jQuery ，当DOM已经加载时，可以跳过 $（document）.ready（function（）{...}）; 。

希望这有助于。

So I recently bought and downloaded a template from ThemeForest. I set up the template on my local server. I generated the navigation, which has dropdown menus, with codeigniter. I had everything in the menu coded correctly. I only had the header generated and went to test it out and realized the dropdown menus were not working. I spent about two hours trying to figure out what was wrong with my code. Then I finally realized that the JavaScript files were included in the footer of the template... which I had not yet generated.

So my question is... why would someone put JavaScript files in the footer of an HTML page? I thought that JS was only supposed to be located in the header of the file. Right?

解决方案

There are different ways you could load a script file to a web page.

But loading scripts at bottom of you page have the following advantages.

1. Will not block any DOM content to be loaded.
2. All the DOM elements will be available for the scripts that are being loaded.
3. If you are using third-party libraries such as jQuery, you can skip the $(document).ready(function () {...}); as the DOM is already loaded.

Hope this helps.

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