What does |0 do in Javascript?

Question

I have been looking into asm.js to use for a project recently, and I noticed that very often the asm.js compiled code will end a statement with |0;, even seemingly redundantly as in the statement i = i|0;

This is not something I have encountered in Javascript code before. What is it for?

EDIT

I don't believe this is duplicate. I know what a bitwise or is. I am specifically asking here why one might use it to or with a 0 before assignment. What purpose does that serve?

just see doc: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators#Bitwise_OR — Grundy, Oct 27 '15 at 11:52
@Grundy I know what a bitwise or is. I just didn't understand the purpose of it in this case. — Luke, Oct 27 '15 at 11:53
from doc: _Bitwise ORing any number x with 0 yields x. Bitwise ORing any number x with -1 yields -1._ — Grundy, Oct 27 '15 at 11:55
This is not a duplicate question. Bitwise OR with 0 is more specific than bitwise OR. And the accepted answer explains that. — Todd Chaffee, Aug 16 '19 at 13:34

score 6 · Accepted Answer · answered Oct 27 '15 at 11:52

6

Convert to integer and apply a bitwise or with 0. Basically a short form of Math.floor().

answered Oct 27 '15 at 11:52

Nina Scholz

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Note that `undefined` `NaN` and `null` are also turned into `0` with this! :-) – Stephan Bijzitter Oct 27 '15 at 11:55

What does |0 do in Javascript?

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