`Math.trunc` VS`| 0` VS`＆LT;＆LT; 0` VS`＆GT;＆GT; 0` VS`＆放大器; -1` VS`^ 0` [英] `Math.trunc` vs `|0` vs `<<0` vs `>>0` vs `&-1` vs `^0`

问题描述

我刚刚发现，在ES6有一个新的数学方法： Math.trunc

我看了它在 MDN文章描述，它听起来就像使用 | 0

此外，＆LT;＆LT; 0 ，＆GT;＆GT; 0 ，＆放-1 ， ^ 0 也在做类似的事情（感谢@kojiro＆安培; @Bergi）。

一些测试后，似乎唯一的区别是：

• Math.trunc 收益 -0 在区间数（ - 1， - 0] 位运算符 0 。


• Math.trunc 收益 NaN的与非数字。位运算符返回 0 。

是否有更多的差异（其中所有的人）？

---

  N | Math.trunc |位运算符
----------------------------------------
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
为NaN |为NaN | 0
富|为NaN | 0
无效（0）|为NaN | 0
 

解决方案

如何 Math.trunc（Math.pow（2,31））与 Math.pow（2,31）| 0

位运算是在符号的32位整数进行。所以，当你做Math.pow（2，31）你在比特10000000000000000000000000000000这种重新presentation。因为这个数字已被转换为符号的32位的形式，我们现在的符号位的位置有一个1。这意味着，我们在签订的32位形式寻找一个-eve数。然后，当我们做位或为0，我们得到符号32位形式同样的事情。在十进制是-2147483648。

边注：的在签约的32位形成可以被重新二进制psented为$ P $是[10000000000000000000000000000000，01111111111111111111111111111111]小数的范围。在十进制（基数为10）这个范围是[-2147483648，2147483647]。

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

解决方案

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].

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