Ways to add javascript files dynamically in a page

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I have seen Scriptaculous.js file to include its required javascript files dynamically. Is there any better approach to include javascript dynamically.

For example,

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[愿得一人]

2020-11-28 09:38
there are many different ways, but the way Google loads additional scripts is like this:
```
function getScript(src) {
    document.write('<' + 'script src="' + src + '"' +
                   ' type="text/javascript"><' + '/script>');
}
```
This is taken directly from Google maps loader.

Writing a script tag directly to the document is the simplest and most efficient way.
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旧时难觅i

2020-11-28 09:41

We can quickly extend this so that a callback can be performed once the script is added.

function loadjscssfile(filename, filetype, callback){
    if (typeof fileref!="undefined") {
        document.getElementsByTagName("head")[0].appendChild(fileref);
        callback();
    }
}

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粉色の甜心

2020-11-28 09:47
I've seen what the scriptaculous loader does. What it does is that it goes through all script tags in the document to find the one that loaded itself, e.g:
```
<script src="/path/to/single.js?files=first.js,second.js,third.js"></script>
```
Then it parses the querystring used inside the src attribute and dynamically create additional script tags for each script file. At the same time it also parses the path of the base script (/path/to/single.js) and uses the same path to load dependency files (e.g. /path/to/first.js).

You can create your own script loader like this. In vanilla javascript, you can use the following functions:
- getElementsByTagName -- find all scripts
- getAttribute -- find src/href/type attribute
- createElement -- create a script element
- appendChild -- append to head/body
Anand Thangappan has posted a solution that uses these functions. If you're using a framework such as jQuery or MooTools then both provide their own implementations of dynamically loading JsvaScript.

Finally, there is a server side solution for your problem. Look at minify -- Combines and minifies multiple CSS or JavaScript files into a single download.
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生来不讨喜

2020-11-28 09:49

You can use the jQuery.getScript() function... I think it will be much easier to you with this to include a JavaScript .js file.

Here is the reference.

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清歌不尽

2020-11-28 09:50

Following the advice of Salaman A's comments, I found how Google does it now with Analytics: https://developers.google.com/analytics/devguides/collection/gajs/asyncTracking

And here is a more generic version of the same code:

(function() {
    var s = document.createElement('script'); // Create a script element
    s.type = "text/javascript";               // optional in html5
    s.async = true;                           // asynchronous? true/false
    s.src = "//example.com/your_script.js"; 
    var fs = document.getElementsByTagName('script')[0];  // Get the first script
    fs.parentNode.insertBefore(s, fs);
})();

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天涯浪人

2020-11-28 09:53

document.getElementsByTagName("head")[0].appendChild(fileref‌) is not working if you have some document.ready() works inline. $("head").append(fileref); works great for me, although it needs jquery.min.js inline reference.

<head>
    <!-- Meta, title, CSS, favicons, etc. -->
    <script src="script/jquery.min.js"></script>
    <script src="script/master_load.js"></script>
    <script>
        load_master_css();
        load_master_js();
    </script>
</head>

and master_load.js :

function loadjscssfile(filename) {
    if (filename.substr(filename.length - 4) == ".css") { // 'endsWith' is not IE supported.
        var fileref = document.createElement("link")
        fileref.setAttribute("rel", "stylesheet")
        fileref.setAttribute("href", filename)
        //fileref.setAttribute("type", "text/css")
    }
    else if (filename.substr(filename.length - 3) == ".js") {
        var fileref = document.createElement('script')
        fileref.setAttribute("src", filename)
        //fileref.setAttribute("type", "text/javascript")
    }
    $("head").append(fileref);
}
function load_master_css() {
    loadjscssfile("css/bootstrap.min.css");
    // bunch of css files
}
function load_master_js() {
    loadjscssfile("script/bootstrap.min.js");
    // bunch of js files
}

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