What is the JavaScript >>> operator and how do you use it?

Question

I was looking at code from Mozilla that add a filter method to Array and it had a line of code that confused me.

var len = this.length >>> 0;
         


        

Answer 1

Two reasons:

1. The result of >>> is an "integral"

2. undefined >>> 0 = 0 (since JS will try and coerce the LFS to numeric context, this will work for "foo" >>> 0, etc. as well)

Remember that numbers in JS have an internal-representation of double. It's just a "quick" way of basic input sanity for length.

However, -1 >>> 0 (oops, likely not a desired length!)