Repeating a string n times in javascript.

This is without Javascript Harmony.

function repeat(str, n){
  if(n <= 0 || str.length === 0){
    return '';
  }
  if(n === Infinity){
    throw new RangeError("I cannot repeat a string Infinity times!");
  }
  n = Math.floor(+n);
  var nstr = '';
  for(var i = 0; i < n; i++){
    nstr += str;
  }
}