Script async Property

Find out if a script was executed asynchronously as soon as it was available:

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

The result of x will be:

true

Definition and Usage

The async property sets or returns whether a script should be executed asynchronously as soon as it is available, or not.

This property reflects the async attribute of the <script> tag.

Note: The async attribute is only for external scripts (and should only be used if the src attribute is present).

Note: There are several ways an external script can be executed:

If async is present: The script is executed asynchronously with the rest of the page (the script will be executed while the page continues the parsing)
If async is not present and defer is present: The script is executed when the page has finished parsing
If neither async or defer is present: The script is fetched and executed immediately, before the browser continues parsing the page

The async property is supported in all major browsers.

Note: The async property is not supported in IE 9 and earlier versions, and in Opera 12 and earlier versions.

Return the async property:

scriptObject.async

Set the async property:

scriptObject.async=true|false

Value	Description
true\|false	Specifies whether a script should be executed asynchronously as soon as it is available, or not 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

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