Javascript pipe in math to get Math.floor without using Math.floor

Question

I just saw this shortcut being used in some JavaScript.

(9 + 2) / 2|0; // results in 5

When you do the normal math it results in 5.5.

How come the top expression is resulting in Math.floor((9+2)/2)? Can someone point in in the direction of what that pipe is doing, I don't understand the shortcut.

Have a look at this question: http://stackoverflow.com/questions/7487977/using-bitwise-or-0-to-floor-a-number — Calum, Aug 31 '16 at 02:07
[List of JS operators...](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators) — nnnnnn, Aug 31 '16 at 02:14

score 3 · Answer 1 · answered Aug 31 '16 at 02:10

Firstly the result of (9+2)/2 is 5.5 in JavaScript
Then it's applied a bitwise Or operation. For JavaScript, the bitwise operations don't work directly on the 64-bit representations. Instead, the value is converted into a 32-bit integer, which means 5.5 to 5, then the result of 5|0 is 5.

score 3 · Accepted Answer · answered Aug 31 '16 at 02:11

A single pipe | is BitWise OR.
Bitwise operator only allow integer values, so after decimal point value is discarded.

Bitwise OR operator | takes 2 bit patterns, and perform OR operations on each pair of corresponding bits.
The following example will explain it.

1010                            
1100       
----------bitwise or
1110

Javascript pipe in math to get Math.floor without using Math.floor

2 Answers2