GlobalEventHandlers.onkeydown - Web APIs 编辑

The onkeydown property of the GlobalEventHandlers mixin is an EventHandler that processes keydown events.

The keydown event fires when the user presses a keyboard key.

Syntax

target.onkeydown = functionRef;

Value

functionRef is a function name or a function expression. The function receives a KeyboardEvent object as its sole argument.

Example

This example logs the KeyboardEvent.code value whenever you press down a key inside the <input> element.

HTML

<input>
<p id="log"></p>

JavaScript

const input = document.querySelector('input');
const log = document.getElementById('log');

input.onkeydown = logKey;

function logKey(e) {
  log.textContent += ` ${e.code}`;
}

Result

Specifications

Browser compatibility

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Compatibility notes

Since Firefox 65, the keyup and keydown events are now fired during IME composition, to improve cross-browser compatibility for CJKT users (bug 354358, also see keydown and keyup events are now fired during IME composition for more useful details). To ignore all keydown events that are part of composition, do something like this (229 is a special value set for a keyCode relating to an event that has been processed by an IME):

eventTarget.addEventListener("keydown", event => {
  if (event.isComposing || event.keyCode === 229) {
    return;
  }
  // do something
});

See also

• keydown event
• Related event handlers
  • GlobalEventHandlers.onkeypress
  • GlobalEventHandlers.onkeyup