The answer
Use rest parameters: myBind = function(context, ...presetArgs). Spread them in the call: fn.call(context, ...presetArgs, ...laterArgs). This merges preset and later arguments.
How to Write a Polyfill for bind in JavaScript
How do you support preset arguments in a bind polyfill?
More FAQs in How to Write a Polyfill for bind in JavaScript
Function.prototype.myBind = function(context, ...presetArgs) { const fn = this; return function(...laterArgs) { return fn.call(context, ...presetArgs, ...laterArgs); }; }.
Check this instanceof boundFn. If true (called with new), use new fn(...args) instead of fn.call(context, ...args). Set boundFn.prototype = Object.create(fn.prototype).
So that instances created with new boundFn() have the correct prototype chain. Without it, instanceof checks would fail. Set boundFn.prototype = Object.create(fn.prototype).
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