I have the following code that will run when an iframe webapplet is loaded in the current page.

window.addEventListener("keydown", function(e) {
if(["Backspace","Tab","Enter","ShiftLeft","ShiftRight","ControlLeft","ControlRight","AltLeft","AltRight","Pause","CapsLock","Escape","Space","PageUp","PageDown","End","Home","ArrowLeft","ArrowUp","ArrowRight","ArrowDown","PrintScreen","Insert,","Delete","Digit0","Digit1","Digit2","Digit3","Digit4","Digit5","Digit6","Digit7","Digit8","Digit9","KeyA","KeyB","KeyC","KeyD","KeyE","KeyF","KeyG","KeyH","KeyI","KeyJ","KeyK","KeyL","KeyM","KeyN","KeyO","KeyP","KeyQ","KeyR","KeyS","KeyT","KeyU","KeyV","KeyW","KeyX","KeyY","KeyZ","MetaLeft","MetaRight","ContextM,nu","Numpad0","Numpad1","Numpad2","Numpad3","Numpad4","Numpad5","Numpad6","Numpad7","Numpad8","Numpad9","NumpadMultiply","NumpadAdd","NumpadSubtract","NumpadDecimal","NumpadDivide","F1","F2","F3","F4","F5","F6","F7","F8","F9","F10","F11","F12","NumLock","ScrollLock","Semicolon","Equal","Comma","Minus","Period","Slash","Backquote","BracketLeft","Backslash","BracketRight","Quote"].indexOf(e.code) > -1) {
    e.preventDefault();
}
}, false);

What I’d like to do is easily undo the above code once the user closes the webapplet. This will simply set the webapp to display: none, so no page load happens.

I’m sure there’s a way to label the eventlistener and then call removeEventListener, but I’m struggling to find the right solution.

>Solution :

function handleKey(e) {
if(["Backspace","Tab","Enter","ShiftLeft","ShiftRight","ControlLeft","ControlRight","AltLeft","AltRight","Pause","CapsLock","Escape","Space","PageUp","PageDown","End","Home","ArrowLeft","ArrowUp","ArrowRight","ArrowDown","PrintScreen","Insert,","Delete","Digit0","Digit1","Digit2","Digit3","Digit4","Digit5","Digit6","Digit7","Digit8","Digit9","KeyA","KeyB","KeyC","KeyD","KeyE","KeyF","KeyG","KeyH","KeyI","KeyJ","KeyK","KeyL","KeyM","KeyN","KeyO","KeyP","KeyQ","KeyR","KeyS","KeyT","KeyU","KeyV","KeyW","KeyX","KeyY","KeyZ","MetaLeft","MetaRight","ContextM,nu","Numpad0","Numpad1","Numpad2","Numpad3","Numpad4","Numpad5","Numpad6","Numpad7","Numpad8","Numpad9","NumpadMultiply","NumpadAdd","NumpadSubtract","NumpadDecimal","NumpadDivide","F1","F2","F3","F4","F5","F6","F7","F8","F9","F10","F11","F12","NumLock","ScrollLock","Semicolon","Equal","Comma","Minus","Period","Slash","Backquote","BracketLeft","Backslash","BracketRight","Quote"].indexOf(e.code) > -1) {
    e.preventDefault();
}
}

window.addEventListener("keydown", handleKey, false);

Removing:

window.removeEventListener("keydown", handleKey, false);