Script async attribute

HTML DOM Script Object

Definition and Usage

async the attribute settings or returns whether the script should be executed asynchronously as soon as it is available.

This attribute reflects <script> tag of async attribute.

Note:The async attribute is only applicable to external scripts (and should only be used when the src attribute is set).

Note:There are several ways to execute external scripts:

  • If async is present: The script is executed asynchronously with the rest of the page (the script will be executed while the page continues to parse)
  • If async is not present and defer is present: Execute the script when the page parsing is complete
  • If neither async nor defer is present: Fetch and execute the script immediately before the browser continues parsing the page

See also:

HTML Reference Manual:HTML <script> async Attribute

HTML Reference Manual:HTML <script> Tag

Example

Check if the script is executed asynchronously as soon as it is available:

var x = document.getElementById("myScript").async

Try it yourself

Syntax

Return the async attribute:

scriptObject.async

Set the async attribute:

scriptObject.async = true|false

Attribute value

Value Description
true|false

Specify whether the script should be executed asynchronously as soon as it is available.

  • true - The script will be executed asynchronously as soon as it is available
  • false - The script will not be executed asynchronously as soon as it is available.

Technical Details

Return Value: Boolean value, returns true if the script is executed asynchronously as soon as it is available; otherwise returns false.

Browser Support

The numbers in the table indicate the first browser version to fully support this attribute.

Chrome Edge Firefox Safari Opera
Chrome Edge Firefox Safari Opera
Support 10.0 Support Support Support

HTML DOM Script Object