The keyup event is fired when a key is released.
The keydown and keyup events provide a code indicating which key is pressed, while keypress indicates which character was entered. For example, a lowercase "a" will be reported as 65 by keydown and keyup, but as 97 by keypress. An uppercase "A" is reported as 65 by all events.
Note: If you're looking for a way to react to changes in an input's value, you should use the input event. Some changes are not detectable by keyup, for example pasting text from the context menu in a text input.
This example logs the KeyboardEvent.code value whenever you release a key.
<p>Focus the IFrame first (e.g. by clicking in it), then try pressing some keys.</p>
<p id="log"></p>
const log = document.getElementById('log');
document.addEventListener('keyup', logKey);
function logKey(e) {
log.textContent += `${e.code}`;
}
document.onkeyup = logKey;
An Input Method Editor (IME) is a program that enables users to enter characters that are not supported by their keyboard using some other key combination.
Since Firefox 65, the keydown and keyup events are now fired during IME composition, to improve cross-browser compatibility for CJKT users (bug 354358. To ignore all keyup 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("keyup", event => {
if (event.isComposing || event.keyCode === 229) {
return;
}
});