How to Remove Listener from addEventListener Method and on- Event Handler

addEventListener: Using removeEventListener

For the structure of addEventListener, here's the documentation at MDN EventTarget: addEventListener

For the structure of removeEventListener, here's the documentation at MDN EventTarget: removeEventListener

Let's use click event for this example.

// The button element. const myButton = document.getElementById("myButton"); // The function being invoked for the click event of an element (button). const clickFunction = (e) => { console.log("CLICK!"); console.log(e); }; // Assign the trigger for the button: addEventListener. const assignClickTrigger = () => { myButton.addEventListener("click", clickFunction); }; // Remove the trigger from the button: removeEventListener. const removeClickTrigger = () => { myButton.removeEventListener("click", clickFunction); }; /* // Now we can use assignClickTrigger and removeClickTrigger. // For activating the listener, we do: assignClickTrigger(); // For DEACTIVATING the listner, we do: removeClickTrigger(); */

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on- Event

Let's use the similar click event for this example. Thus, it will be onclick.

For the structure of onclick event, here's the reference at MDN Element: click event

// The button element. const myButton = document.getElementById("myButton"); // The function being invoked for the click event of an element (button). const clickFunction = (e) => { console.log("CLICK!"); console.log(e); }; // Assign the trigger for the button. const assignClickTrigger = () => { myButton.onclick = clickFunction; }; // Remove the trigger from the button. const removeClickTrigger = () => { myButton.onclick = null; /* It can also be: myButton.onclick = ""; // Or: myButton.onclick = undefined; // But, for the intention consistency, to nullify the listener, // it is recommended to reassign using null. */ }; /* // Now we can use assignClickTrigger and removeClickTrigger. // For activating the listener, we do: assignClickTrigger(); // For DEACTIVATING the listner, we do: removeClickTrigger(); */

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Why Do We Need to Remove the Listener?

1. Prevent Memory Leaks: Detached DOM elements with active listeners can consume memory unnecessarily.
2. Improve Performance: Unused listeners may slow down the application, especially in dynamic or large-scale environments.
3. Avoid Unintended Behavior: Listeners left active can cause unexpected or duplicate actions, leading to bugs.
4. Clean Up Resources: Removing listeners ensures proper resource management in single-page applications or when reusing components.

I had the issues back then. It was because the elements were dynamically generated, and the event listeners were assigned after the elements were rendered. The assignments kept piling up without proper clean up.

Also, it happened on a static single element. Such as video, or audio element. If the src was dynamically modified and we didn't properly clean up the listener, that would run into unnecessary unpredictabilities.

By cleaning up listeners when they’re no longer needed, we will keep our code efficient and predictable^{Exclamation mark}

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