Simple Tips and Code to Load External JavaScript, CSS Files Dynamically

This JavaScript article tutorial guides you how to build a simple JavaScript function for loading JavaScript and CSS external files dynamically. No new thing but this JavaScript snippet is still a good way to make your website become more comfortable.


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Generally we includes an external css ( Cascading Style Sheets ) and js ( javascript ) files in the HEAD section of our HTML page. We include them by following conventional method -

1<link rel="stylesheet" type="text/css" href="stylesheet/mycss.css"/>
2<script language="javascript" src="javascript/myjs.js" type="text/javascript"></script>

This method added files to the page as they encountered in page source code or synchronously.

Here we will learn how to dynamically load an external file in simple steps.

1. For loading .js or .css file dynamically we use DOM methods to first create new “script” or “link” element. Assign it to appropriate attributes and then finally use appendChild() function to include it into head section on document tree.

Example :

01function includejscssfiles(filename, filetype)
02{
03    if (filetype=="js") //if filename is an JavaScript file
04    {
05        var fileref=document.createElement('script')
06        fileref.setAttribute("type","text/javascript")
07        fileref.setAttribute("src", filename)
08    }
09    else if (filetype=="css") //if filename is an CSS file
10    {
11        var fileref=document.createElement("link")
12        fileref.setAttribute("rel", "stylesheet")
13        fileref.setAttribute("type", "text/css")
14        fileref.setAttribute("href", filename)
15    }
16    if (typeof fileref!="undefined")
17    document.getElementsByTagName("head")[0].appendChild(fileref)
18}

2. Now we will create one more function that contains file name and file type. In this function we will call includejscssfiles() by passing file name and file type as its parameters.

1function loadfiles()
2{
3    includejscssfiles('mycss.css', 'css');
4    includejscssfiles('myjs.js', 'js');
5}

3. Call loadfiles function on onload on tag. Thats it.

function parameter “filetype” lets you tell the script what file type to expect before loading. After that, the function sets out to create the element using the appropriate DOM methods, assign it the proper attributes, and finally, add it to the end of the HEAD section.

By referencing the HEAD element of the page first and then calling appendChild(), this means the newly created element is added to the very end of the HEAD tag.

Hope this tutorial will help you.

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