Comparing the performance of Math.floor(), parseInt and a (bitwise) shift

I read somewhere that a bitwise left shift was a faster method of removing a fraction of a floating point number in Javascript than using parseInt or Math.floor(). I wasn't surprised that parseInt was slow, since I think it parses the number as a string, but the left shift being faster than Math.floor() was a bit more puzzling to me. So I decided to make a JSPerf test to compare those three methods. Read on for the full results