Why did React class components need bind for event handlers in JavaScript?
Because React passes event handlers as regular functions (detached from the instance). Without bind, this is not the component. Fix with bind in the constructor or arrow class fields. Modern React uses hooks (function components), which avoid this issue.
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More FAQs in this in ES6 Classes in JavaScript
this in the constructor is the new instance. this in methods is the instance when called as instance.method(). But detaching a method (passing to setTimeout or addEventListener) loses this. Fix with bind, arrow class fields, or arrow wrappers.
Because the method is detached from the instance when passed as a reference. The callback is called as a plain function, so this is not the instance. Fix by binding in the constructor or using arrow class fields.
Three ways: bind in the constructor (this.handleClick = this.handleClick.bind(this)), use arrow class fields (handleClick = () => { ... }), or use arrow wrappers in callbacks (setTimeout(() => this.method(), 1000)).
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