Algorithm to determine if brackets are balanced in a string

Brackets Balanced

function balanced(str){
  var opens = ['{','(','['],
      closes = ['}',')',']'],
      split = str.split(''),
      stack = [];

  for (var i = 0; i < split.length - 1; i++){
    if (opens.indexOf(split[i]) >= 0){
      stack.push(split[i]);
    } else if (closes.indexOf(split[i]) >= 0) {
      var pop = stack.pop();
      if (opens.indexOf(pop) !== closes.indexOf(split[i]) || stack.length == 0){
        return false;
      }
    }
  }

  return true;
}