The MouseEvent.altKey read-only property is a boolean value that indicates whether the alt key was pressed or not when a given mouse event occurs.
Be aware that the browser can't always detect the alt key on some operating systems. On some Linux variants, for example, a left mouse click combined with the alt key is used to move or resize windows.
Note: On Macintosh keyboards, this key is also known as the option key.
A boolean value, where true indicates that the key is pressed, and false indicates that the key is not pressed.
This example logs the altKey property when you trigger a click event.
html
<p>Click anywhere to test the <code>altKey</code> property.</p>
<p id="log"></p>
js
let log = document.querySelector("#log");
document.addEventListener("click", logKey);
function logKey(e) {
log.textContent = `The alt key is pressed: ${e.altKey}`;
}
| Specification |
|---|
| UI Events # dom-mouseevent-altkey |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
altKey |
1 | 12 | 1.5 | 9 | ≤12.1 | 1 | ≤37 | 18 | 4 | ≤12.1 | 1 | 1.0 |
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https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/altKey