UIEvent.which

Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The UIEvent.which read-only property of the UIEvent interface returns a number that indicates which button was pressed on the mouse, or the numeric keyCode or the character code (charCode) of the key pressed on the keyboard.

Value

Value for KeyboardEvent Non-Standard

For KeyboardEvent, event.which contains the numeric code for a particular key pressed, depending on whether an alphanumeric or non-alphanumeric key was pressed. Please see deprecated KeyboardEvent.charCode and KeyboardEvent.keyCode for more details.

Note: Consider KeyboardEvent.key or KeyboardEvent.code for new code.

Value for MouseEvent Non-Standard

For MouseEvent, event.which is a number representing a given button:

  • 0: No button
  • 1: Left button
  • 2: Middle button (if present)
  • 3: Right button

For a mouse configured for left-handed use, the button actions are reversed. In this case, the values are read from right to left.

Note: Consider MouseEvent.button for new code.

Examples

<html>
<head>
<title>charCode/keyCode/which example</title>

<script type="text/javascript">

function showKeyPress(evt) {
alert("onkeypress handler: \n"
      + "keyCode property: " + evt.keyCode + "\n"
      + "which property: " + evt.which + "\n"
      + "charCode property: " + evt.charCode + "\n"
      + "Character Key Pressed: "
      + String.fromCharCode(evt.charCode) + "\n"
     );
}

function keyDown(evt) {
alert("onkeydown handler: \n"
      + "keyCode property: " + evt.keyCode + "\n"
      + "which property: " + evt.which + "\n"
     );
}

</script>
</head>

<body
 onkeypress="showKeyPress(event);"
 onkeydown="keyDown(event);"
>

<p>Please press any key.</p>

</body>
</html>

Specifications

Specification
UI Events
# dom-uievent-which

Browser compatibility

BCD tables only load in the browser

See also