🔰remove handler

JS ⟩ browser ⟩ event ⟩ handler ⟩ register ⟩ remove

🧨 雷區

If you want to remove a capturing event handler, you must also pass true as the third argument to removeEventListener().

To remove a handler we need exactly the same function as was assigned.

// ❌ this won't work❗️ 
// ⭐️ same code but different functions ↴
//                                ╭────────────────────╮
elem.addEventListener   ("click", () => alert('Thanks!'));
elem.removeEventListener("click", () => alert('Thanks!'));

// ✅ the right way
//                    same function ↴
function handler(){ ... }    //   ╭─────╮
elem.addEventListener   ("click", handler);
elem.removeEventListener("click", handler);

🔴 主題

• removing a capturing handler