What does the "|" (single pipe) do in JavaScript?

Question

console.log(0.5 | 0); // 0
console.log(-1 | 0);  // -1
console.log(1 | 0);   // 1

Why does 0.5 | 0 return zero, but any integer (including negative) returns the input integer? What does the single pipe ("|") do?

Answer 1

This is a bitwise or.
Since bitwise operations only make sense on integers, 0.5 is truncated.

x | 0 is x, if x is an integer.