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Why must you pass the same function reference to removeEventListener?

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01

Understand the problem

Explain listener removal.

events
02

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04

Read the code

Why inline removal fails, and the fixes
// WRONG — a brand-new function each time, so removal does nothing
el.addEventListener("click", () => doThing());
el.removeEventListener("click", () => doThing());  // no-op: different reference

// RIGHT — keep ONE reference and reuse it
const handler = () => doThing();
el.addEventListener("click", handler);
el.removeEventListener("click", handler);          // removed ✓

// .bind() also returns a NEW function — store it if you must remove it
const bound = obj.method.bind(obj);
el.addEventListener("click", bound);
el.removeEventListener("click", bound);

// modern alternatives
el.addEventListener("click", onceFn, { once: true });   // auto-removes
const ctrl = new AbortController();
el.addEventListener("click", a, { signal: ctrl.signal });
el.addEventListener("scroll", b, { signal: ctrl.signal });
ctrl.abort();                                           // removes BOTH
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