Question

in my html, I’ve got an event binding as below:

document.addEventListener('keydown', onKeyDown);

Now that I’d like to hook on the keydown event, i.e., when keydown happens, call another function and trigger the onKeyDown manually.

the document.addEventListener('keydown', onKeyDown); is already there(upstream) and I don’t want to change it. so to sum up:

`keydown` -> `do something` -> `onKeyDown`

Is there a way to achieve this?

Answer 1

If your onKeyDown method could be accessed, you can remove it from event listeners and reattach a modified version:

function myKeyDown() {
    // your logic
    onKeyDone.apply(this, arguments);
}
document.addEventListener('keydown', myKeyDown);
document.removeEventListener('keydown', onKeyDown);