JavaScript 三重大于
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JavaScript triple greater than
提问by Jey Balachandran
I saw this syntax on another StackOverflow postand was curious as to what it does:
我在另一个StackOverflow 帖子上看到了这种语法，并且很好奇它的作用：
var len = this.length >>> 0;
var len = this.length >>> 0;
What does >>>imply?
是什么>>>暗示？
采纳答案by Joe
That's an unsigned right shift operator. Interestingly, it is the only bitwise operatorthat is unsignedin JavaScript.
那是一个无符号的右移运算符。有趣的是，它是唯一位运算符是无符号在JavaScript中。
The >>> operator shifts the bits of expression1 right by the number of bits specified in expression2. Zeroes are filled in from the left. Digits shifted off the right are discarded.
>>> 运算符将 expression1 的位右移 expression2 中指定的位数。从左边开始填零。丢弃右移的数字。
回答by Eric
Ignoring its intended meaning, this is most likely where you'll see it used:
忽略其预期含义，这很可能是您看到它使用的地方：
>>> 0is unique in that it is the only operator that will convert any type to a positive integer:
>>> 0它的独特之处在于它是唯一将任何类型转换为正整数的运算符：
"string" >>> 0 == 0
(function() { }) >>> 0 == 0
[1, 2, 3] >>> 0 == 0
Math.PI >>> 0 == 3
In your example, var len = this.length >>> 0, this is a way of getting an integer length to use to iterate over this, whatever type this.lengthmay be.
在您的示例中var len = this.length >>> 0，这是一种获取整数长度以用于迭代的方法this，无论类型this.length是什么。
Similarly, ~~xcan be used to convert any variable into a signed integer.
同样，~~x可用于将任何变量转换为有符号整数。
回答by Mark Byers
That operator is a logical right shift. Here the number is shifted 0 bits. A shift of zero bits mathemetically should have no effect.
该运算符是逻辑右移。这里的数字被移动了 0 位。数学上的零位移位应该没有影响。
But here it is used to convert the value to an unsigned 32 bit integer.
但在这里它用于将值转换为无符号的 32 位整数。
回答by nrabinowitz
>>>is a bit-wise operator, zero-fill right shift.
>>>是一个按位运算符，零填充右移。
I think the only effect of >>> 0on a positive number is to round down to the nearest integer, same as Math.floor(). I don't see why this would be necessary in your example, as generally a .lengthproperty (e.g. of an Array) would be an integer already.
我认为>>> 0对正数的唯一影响是向下舍入到最接近的整数，与Math.floor(). 我不明白为什么这在您的示例中是必要的，因为通常.length属性（例如 an Array）已经是一个整数。
I've also seen the slightly shorter ~~used in the same way: ~~9.5 == 9; // true.
我还看到了~~以相同方式使用的稍短的：~~9.5 == 9; // true.
