Window.alert()

window.alert() instructs the browser to display a dialog with an optional message, and to wait until the user dismisses the dialog.

Under some conditions — for example, when the user switches tabs — the browser may not actually display a dialog, or may not wait for the user to dismiss the dialog.

Syntax

window.alert(message);

Parameters

message Optional
A string you want to display in the alert dialog, or, alternatively, an object that is converted into a string and displayed.

Example

window.alert("Hello world!");
alert("Hello world!");

Both produce:

Notes

The alert dialog should be used for messages which do not require any response on the part of the user, other than the acknowledgement of the message.

The following text is shared between this article, DOM:window.prompt and DOM:window.confirm Dialog boxes are modal windows - they prevent the user from accessing the rest of the program's interface until the dialog box is closed. For this reason, you should not overuse any function that creates a dialog box (or modal window).

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'alert()' in that specification.
Living Standard

Browser compatibility

BCD tables only load in the browser

See also