KeyboardEvent keyCode Property

Posted 2020-10-07 dazzlinglight

Definition and Usage

The keyCode property returns the Unicode character code of the key that triggered the onkeypress event, or the Unicode key code of the key that triggered the onkeydown or onkeyup event.

The difference between the two code types:

• Character codes - A number which represents an ASCII character
• Key codes - A number which represents an actual key on the keyboard

These types do not always mean the same thing; for example, a lower case "w" and an upper case "W" have the same keyboard code, because the key that is pressed on the keyboard is the same (just "W" = the number "87"), but a different character code because the resulting character is different (either "w" or "W", which is "119" or "87") - See "More Examples" below to better understand it.

Tip: To find out if the user is pressing a printable key (e.g. "a" or "5"), it is recommended to use this property on the onkeypress event. To find out if the user is pressing a function key (e.g. "F1", "CAPS LOCK" or "Home") use the onkeydown or onkeyup event.

Note: In Firefox, the keyCode property does not work on the onkeypress event (will only return 0). For a cross-browser solution, use the which property together with keyCode, e.g:

which

Tip: For a list of all Unicode characters, please study our Complete Unicode Reference.

Tip: If you want to convert the returned Unicode value into a character, use the fromCharCode() method.

Note: This property is read-only.

Note: Both the keyCode and which property is provided for compatibility only. The latest version of the DOM Events Specification recommend using the key property instead (if available).

Tip: If you want to find out whether the "ALT", "CTRL", "META" or "SHIFT" key was pressed when a key event occured, use the altKey, ctrlKey, metaKey or shiftKeyproperty.

 

Example

Using onkeypress and onkeydown to demonstrate the differences between character codes and keyboard codes:

<input type="text" onkeypress="uniCharCode(event)" onkeydown="uniKeyCode(event)"> 

function uniCharCode(event) {
    var char = event.which || event.keyCode;
    document.getElementById("demo").innerhtml = "Unicode CHARACTER code: " + char;
}

function uniKeyCode(event) {
    var key = event.keyCode;
    document.getElementById("demo2").innerHTML = "Unicode KEY code: " + key;
}

When pressing the "a" key on the keyboard (not using caps lock), the result of char and key will be:

Unicode CHARACTER code: 97
Unicode KEY code: 65

https://www.w3schools.com/jsref/event_key_keycode.asp请参考官方网站