15 November 2014 tagged: programming javascript stackoverflow  

How to get the current script element:

This article was originally published as a Stackoverflow answer.

1. Use document.currentScript

document.currentScript will return the <script> element whose script is currently being processed.

<script>
var me = document.currentScript;
</script>

Benefits

  • Simple and explicit. Reliable.
  • Don’t need to modify the script tag
  • Works with asynchronous scripts (defer & async)
  • Works with scripts inserted dynamically

Problems

  • Will not work in older browsers and IE.

2. Select script by id

Giving the script an id attribute will let you easily select it by id from within using document.getElementById().

<script id="myscript">
var me = document.getElementById('myscript');
</script>

Benefits

  • Simple and explicit. Reliable.
  • Almost universally supported
  • Works with asynchronous scripts (defer & async)
  • Works with scripts inserted dynamically

Problems

  • Requires adding a custom attribute to the script tag
  • id attribute may cause weird behaviour for scripts in some browsers for some edge cases

3. Select the script using a data-* attribute

Giving the script a data-* attribute will let you easily select it from within.

<script data-name="myscript">
var me = document.querySelector('script[data-name="myscript"]');
</script>

This has few benefits over the previous option.

Benefits

  • Simple and explicit.
  • Works with asynchronous scripts (defer & async)
  • Works with scripts inserted dynamically

Problems

  • Requires adding a custom attribute to the script tag
  • HTML5, and querySelector() not compliant in all browsers
  • Less widely supported than using the id attribute
  • Will get around <script> with id edge cases.
  • May get confused if another element has the same data attribute and value on the page.

4. Select the script by src

Instead of using the data attributes, you can use the selector to choose the script by source:

<script src="//example.com/embed.js"></script>

In embed.js:

var me = document.querySelector('script[src="//example.com/embed.js"]');

Benefits

  • Reliable
  • Works with asynchronous scripts (defer & async)
  • Works with scripts inserted dynamically
  • No custom attributes or id needed

Problems

  • Does not work for local scripts
  • Will cause problems in different environments, like Development and Production
  • Static and fragile. Changing the location of the script file will require modifying the script
  • Less widely supported than using the id attribute
  • Will cause problems if you load the same script twice

5. Loop over all scripts to find the one you want

We can also loop over every script element and check each individually to select the one we want:

<script>
var me = null;
var scripts = document.getElementsByTagName("script")
for (var i = 0; i < scripts.length; ++i) {
    if( isMe(scripts[i])){
      me = scripts[i];
    }
}
</script>

This lets us use both previous techniques in older browsers that don’t support querySelector() well with attributes. For example:

function isMe(scriptElem){
    return scriptElem.getAttribute('src') === "//example.com/embed.js";
}

This inherits the benefits and problems of whatever approach is taken, but does not rely on querySelector() so will work in older browsers.

6. Get the last executed script

Since the scripts are executed sequentially, the last script element will very often be the currently running script:

var scripts = document.getElementsByTagName( 'script' );
var me = scripts[ scripts.length - 1 ];

Benefits

  • Simple.
  • Almost universally supported
  • No custom attributes or id needed

Problems

  • Does not work with asynchronous scripts (defer & async)
  • Does not work with scripts inserted dynamically