JavaScript · Senior · Question 17 of 75

How do you implement the observer pattern with browser APIs, without libraries?

✓Correct answer: With EventTarget and CustomEvent: dispatchEvent and addEventListener
2With a MutationObserver subscribed to changes of a JS object
3With Object.observe, built into modern browsers

Explanation

You can extend a class from EventTarget and dispatch new CustomEvent('change', { detail }). Other built-in observers: MutationObserver (DOM changes), IntersectionObserver, ResizeObserver. Object.observe was removed from the standard.

How do you implement the observer pattern with browser APIs, without libraries?

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