Generate an array of any length n returning an array that contains a random sequence with integers 0 to n-1

rndSequence.js

rndSequence = function(length) {
  options = length;
  option_sequence = [];
  for (var i = 0; i < options; i++) {
    if (option_sequence.length === 0) {
        var rnd = Math.floor(Math.random()*options);
        option_sequence.push(rnd);
    }
    else if (option_sequence.length > 0) {
        var rnd = Math.floor(Math.random()*options);
        while (option_sequence.indexOf(rnd) != -1) {
      var rnd = Math.floor(Math.random()*options);
        }
        option_sequence.push(rnd);
    }
  }
  return option_sequence;
}

Usage:
console.log(rndSequence(5)) // random sequence of length 5

[1,3,2,4,0] // e.g.