Some common operations can be made shorter using bitwise operators. Here are some of my favorites.
Rounding off a number
Math.floor(3.5) can be written as 3.5|0. The Bitwise OR operator will make an integer out of the number, and this construct is in fact used in asm.js to denote an integer.
Checking for -1
The Bitwise NOT operator will turn -1 into zero. This makes substring checks with indexOf() a little shorter.