javascript - `Math.trunc` vs `|0` vs `<<0` vs `>>0` vs `&-1` vs `^0`

Question

I have just found that in ES6 there's a new math method: Math.trunc.

I have read its description in MDN article, and it sounds like using |0.

Moreover, <<0, >>0, &-1, ^0 also do similar things (thanks @kojiro & @Bergi).

After some tests, it seems that the only differences are:

• Math.trunc returns -0 with numbers in interval (-1,-0]. Bitwise operators return 0.
• Math.trunc returns NaN with non numbers. Bitwise operators return 0.

Are there more differences (among all of them)?

---

n      | Math.trunc | Bitwise operators
----------------------------------------
42.84  | 42         | 42
13.37  | 13         | 13
0.123  | 0          | 0
0      | 0          | 0
-0     | -0         | 0
-0.123 | -0         | 0
-42.84 | -42        | -42
NaN    | NaN        | 0
"foo"  | NaN        | 0
void(0)| NaN        | 0

Answer 1

How about Math.trunc(Math.pow(2,31)) vs. Math.pow(2,31) | 0

Bitwise operations are performed on signed 32-bit integers. So, when you do Math.pow(2, 31) you get this representation in bits "10000000000000000000000000000000". Because this number has to be converted to signed 32-bit form, we now have a 1 in the sign bit position. This means that we are looking at a -eve number in signed 32-bit form. Then when we do the bitwise OR with 0 we get the same thing in signed 32-bit form. In decimal it is -2147483648.

Side note: In signed 32-bit form the range of decimals that can be represented in binary for is [10000000000000000000000000000000, 01111111111111111111111111111111]. In decimal (base 10) this range is [-2147483648, 2147483647].