运算符“>>”（双箭头）和“|”有什么作用 （单管）在 JavaScript 中是什么意思？

What do the operators ">>" (double arrow) and "|" (single pipe) mean in JavaScript?

提问by benhowdle89

I saw this in some JS code:

我在一些 JS 代码中看到了这一点：

        index = [
            ascii[0] >> 2,
            ((ascii[0] & 3) << 4) | ascii[1] >> 4,
            ((ascii[1] & 15) << 2) | ascii[2] >> 6,
            ascii[2] & 63
        ];

I'd quite like to know what a lot of this means. Specifically ">>", a single pipe "|" and the "&" symbol on the last line?

我很想知道这意味着什么。特别是“>>”，单个管道“|” 最后一行的“&”符号？

Much appreciated!

非常感激！

回答by Niet the Dark Absol

x >> ymeans to shift the bits of xby yplaces to the right (<<to the left).

x >> y手段的位移位x通过y的地方（右侧<<到左侧）。

x | ymeans to compare the bits of xand y, putting a 1in each bit if either xor yhas a 1in that position.

x | y表示比较x和 的位，如果其中一个或在该位置有一个，则在每个位中y放置一个。1xy1

x & yis the same as |, except that the result is 1if BOTH xand yhave a 1.

x & y与 相同|，除了结果是1如果 BOTHx并且y有一个1.

Examples:

例子：

#left-shifting 1 by 4 bits yields 16
1 << 4 = b00001 << 4 = b10000 = 16

#right-shifting 72 by 3 bits yields 9
72 >> 3 = b1001000 >> 3 = b1001 = 9

#OR-ing 
8 | 2 = b1000 | b0010 = b1010 = 10

#AND-ing
6 & 3 = b110 & b011 = b010 = 2

For more information, search Google for "bitwise operators".

有关更多信息，请在Google 中搜索“按位运算符”。

回答by Ry-

>>is a right bitwise shift. It takes the bits and shifts them right nplaces¹. For example, let's examine 35 >> 2:

>>是按位右移。它需要这些位并将它们右移n 个位置¹。例如，让我们检查35 >> 2：

35 = 100011 shift two places
     001000 = 8

And indeed, 35 >> 2 == 8.

确实，35 >> 2 == 8。

---

---

|is a bitwise OR. It takes each bit in each operand and ORs them together. You can envision it as a sort of binary addition, but you don't carry when both top and bottom are 1. For example, here's 5 | 3:

|是按位或。它获取每个操作数中的每一位并将它们组合在一起。你可以把它想象成一种二进制加法，但是当 top 和 bottom 都是1. 例如，这里是5 | 3：

5 = 101
3 = 011
| -----
    111 = 7

And indeed, 5 | 3 == 7.

确实，5 | 3 == 7。

---

---

Finally, &is a bitwise AND. It takes each bit in each operand, except instead of giving 1 if either one bit OR the other is one, it gives 1 if one bit AND the other are both one. For example, here's 5 & 3:

最后，&是按位与。它取每个操作数中的每一位，除非如果一位或另一个是 1，则不是给 1，而是如果一位和另一个都是 1，则给 1。例如，这里是5 & 3：

5 = 101
3 = 011
& -----
    001 = 1

Try it out; 5 & 3 == 1.

试试看; 5 & 3 == 1.

---

---

Some other ones you might want to be aware of are <<, which is a left bitwise shift, and ^, which is an XOR (0 when both bits are the same, 1 if they're different).

您可能想知道的其他一些是<<，这是一个左移，以及^，这是一个异或（当两个位相同时为 0，如果它们不同则为 1）。

_{¹Actually, it's n modulo 32. 1 >> 32is 1. Not sure why.}

_{¹实际上，它是 n 模 32。1 >> 32是1。不知道为什么。}

回答by Kendall Frey

The >>and <<operators are a bitwise shift. For example,

的>>和<<运营商是一个按位偏移。例如，

11 =      00001011
11 << 3 = 01011000 = 88

It is worth noting that m << n = m * 2^nand m >> n = m / 2^n. This is sometimes used to do very efficient multiplication/division by powers of 2.

值得注意的是m << n = m * 2^n和m >> n = m / 2^n。这有时用于进行非常有效的乘法/除以 2 的幂。

The &and |are bitwise and and or respectively.

的&和|是按位和和或分别。

11 =      00001011
28 =      00011100
11 & 28 = 00001000 = 8

11 =      00001011
28 =      00011100
11 | 28 = 00011111 = 31

While I'm at it, I should mention the ^operator, which is not used for power, but for bitwise exclusive-or.

在此期间，我应该提到^运算符，它不用于幂，而是用于按位异或。

11 =      00001011
28 =      00011100
11 ^ 28 = 00010111 = 23

回答by German Latorre

• & (Bitwise AND)
• | (Bitwise OR)
• << (Left shift)
• >> (Sign-propagating right shift)

• &（按位与）
• | （按位或）
• <<（左移）
• >>（符号传播右移）

Examples (from https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators):

示例（来自https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators）：

Bitwise and:

按位和：

     9 (base 10) = 00000000000000000000000000001001 (base 2)
    14 (base 10) = 00000000000000000000000000001110 (base 2)
                   --------------------------------
14 & 9 (base 10) = 00000000000000000000000000001000 (base 2) = 8 (base 10)

Left shift (9 << 2 shifts bits of 9 in binary, 2 bits to the left):

左移（9 << 2 以二进制方式将 9 的位向左移动 2 位）：

     9 (base 10): 00000000000000000000000000001001 (base 2)
                  --------------------------------
9 << 2 (base 10): 00000000000000000000000000100100 (base 2) = 36 (base 10)

回答by Kris Krause

Looks like bitwise operators to me:

对我来说看起来像位运算符：

http://web.eecs.umich.edu/~bartlett/jsops.html

http://web.eecs.umich.edu/~bartlett/jsops.html

Edit: that ascii array was a dead give away... LOL

编辑：那个 ascii 数组是一个死的放弃......大声笑