Script async Property
Example
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
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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
Browser Support
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.
Syntax
Return the async property:
scriptObject.async
Set the async property:
scriptObject.async=true|false
Property Values
| Value | Description |
|---|---|
| true|false |
Specifies whether a script should be executed asynchronously as soon as
it is available, or not
|
Technical Details
| Return Value: | A Boolean, returns true if the script is executed asynchronously as soon as it is available, otherwise it returns false |
|---|
Related Pages
HTML reference: HTML <script> async attribute
Script Object
