Math.floor() | 0

Question

I have often seen this in JavaScript:

var val = (myvar / myothervar) | 0;

Which as far as I understood was one of the many shortcuts to floor a value in JavaScript (like ~~, and >> 0, etc). However, I was looking at a piece of code recently that did this:

var val = Math.floor(myvar/ myothervar)|0;

They used Math.floor() and then also did a bitwise OR with 0. The author did this many times, so it wasn't just a typo they did once. What do you gain by doing both?

For the curious, the code I am referring to can be found here

Answer 1

You might not have thought of:

• Math.floor(NaN) == NaN (ok, not really, but Math.floor(NaN) is NaN)
• Math.floor(NaN) | 0 == 0

Also relevant for Infinity

As pointed out by @apsillers, this is probabably to eliminate Infinitys:

var x = 1;
console.log(Math.floor(1 / x));      // 1
console.log(Math.floor(1 / x) | 0);  // 1
x = 0;
console.log(Math.floor(1 / x));      // Infinity
console.log(Math.floor(1 / x) | 0);  // 0