JavaScript triple greater than

I saw this syntax on another StackOverflow post and was curious as to what it does:

var len = this.length >>> 0;

What does >>> imply?

Solution 1:

Ignoring its intended meaning, this is most likely where you'll see it used:

>>> 0 is unique in that it is the only operator that will convert any type to a positive integer:

"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.length may be.

Similarly, ~~x can be used to convert any variable into a signed integer.

Solution 2:

That's an unsigned right shift operator. Interestingly, it is the only bitwise operator that is unsigned in JavaScript.

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.

Solution 3:

That operator is a logical right shift. Here the number is shifted 0 bits. A shift of zero bits mathemetically should have no effect.

But here it is used to convert the value to an unsigned 32 bit integer.