为什么js里面对浮点数两次按位取反可以得到整数？

Question

如何证明
~~(1.2) === parseInt("1.2",10);// true

Answer 1

取反操作符会将Number类型变量转换为整型。而一个整数取反两次则显然是自身。

6.1.6.1.2 Number::bitwiseNOT ( x )
The abstract operation Number::bitwiseNOT takes argument x (a Number) and returns an integral Number. It performs the following steps when called:

1. Let oldValue be ! ToInt32(x).
2. Return the result of applying bitwise complement to oldValue. The mathematical value of the result is exactly representable as a 32-bit two's complement bit string.

https://tc39.es/ecma262/multi...