<!DOCTYPE html>
<html lang="en">
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<meta charset="UTF-8">
<title>Document</title>
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<script>
({toString:b} = 123);
console.log(b === Number.prototype.toString); // true
console.log(Number.prototype.toString()); // 0
console.log(b()); // Number.prototype.toString is not generic
let num = 456;
console.log(num.b()); // num.b is not a function
</script>
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</html>Why can't b be called as a function?
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Number.prototype.toString standard
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will be thrownDirectly call
thisiswindowYou can use it like this:
You can
b.call(num), and generally speaking, it is easy to accept thattoStringis not allowed to be executed as an ordinary function, just like constructors are generally not executed as ordinary functions.ps: The
Number.prototype.toString()in the example actually has the same scope asNumber.prototypeTo add, the answer is a bit off topic. b() is actually called as a function and the call is successful. The error is thrown by toString() itself.
Number.prototype.toStringcan be called as a function but this must be of type Number. The same applies to other types of toString.15.7.4.2 Number.prototype.toString