Bonfire: Repeat a string repeat a string

My solution:

function repeat(str, num) {
  var singles = [];
  if (num <= 0){
   repeatedStr="";
  }
  for(i=0;i<num;i++){
    singles.push(str);
    repeatedStr = singles.join("");
  }
  return repeatedStr;
}

repeat("abc", 3);

Critics:
- I still make stupid mistakes regarding variables scope and had at first put var singles = []; inside the for loop...
- I repeat myself when instead of directly returning singles.join("") I assign it first to repeatedStr. Only advantage I could see is if we further down the road would want to access this variable.

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Now, FFC on their wiki, have this similar one:

function repeat(str, num) {
  var newstr = [];
  for (var i = 0; i < num; i++) {
    newstr.push(str);
  };
  return newstr.join('');
}

repeat("abc", 3, "");

Ok, it's still a simple one but more elegant, it gets rid of the if condition by inserting the empty string as an argument. Since we havn't seen this in the previous Javascript Waypoints, I assume it means a sort of "false default" value. I've tried to google it but since I don't know how this notation style is named, it's very hard to find something relevant. If anyone got any idea feel free to tell in the comments.