What is this asm style “x | 0” some javascript programmers are now using?

Question

I\'ve seen some performance critical javascript code, like the one on this project that makes extensive use of bitwise OR operations with 0. Ex:

GameBoyAdvan         


        

Answer 1

What it actually does can be seen in this fiddle

It's probing the variable against integer type in this case and either "flooring" or set it to 0 if not an integer.

Thus, there's a tremendous differnece to a = a || 0 which would leave a value of 3.2 untouched.