Fix lost `this` binding in callback registration

intermediate

By FrontendAtlas Editorial · Updated Mar 31, 2026

A teammate passes an object method straight into a callback API, assuming it will still remember its owner later. Direct calls like `tracker.recordClick()` work, but the same method breaks once another function invokes it without the original receiver. Fix the bug so registered callbacks keep the right `this`.

Examples

const tracker = createClickTracker('save');
tracker.recordClick(); // 'save:1'
tracker.attach(handler => handler()); // 'save:2'

const tracker = createClickTracker('open');
tracker.attach(handler => [handler(), handler()]); // ['open:1', 'open:2']