How do I reverse a String in Dart?

Question

I have a String, and I would like to reverse it. For example, I am writing an AngularDart filter that reverses a string. It\'s just for demonstration purposes, but it made me wo

Answer 1

I've made a small benchmark for a few different alternatives:

String reverse0(String s) {
  return s.split('').reversed.join('');
}

String reverse1(String s) {
  var sb = new StringBuffer();
  for(var i = s.length - 1; i >= 0; --i) {
    sb.write(s[i]);
  }
  return sb.toString();
}

String reverse2(String s) {
  return new String.fromCharCodes(s.codeUnits.reversed);
}

String reverse3(String s) {
  var sb = new StringBuffer();
  for(var i = s.length - 1; i >= 0; --i) {
    sb.writeCharCode(s.codeUnitAt(i));
  }
  return sb.toString();
}

String reverse4(String s) {
  var sb = new StringBuffer();

  var i = s.length - 1;

  while (i >= 3) {
    sb.writeCharCode(s.codeUnitAt(i-0));
    sb.writeCharCode(s.codeUnitAt(i-1));
    sb.writeCharCode(s.codeUnitAt(i-2));
    sb.writeCharCode(s.codeUnitAt(i-3));
    i -= 4;
  }

  while (i >= 0) {
    sb.writeCharCode(s.codeUnitAt(i));
    i -= 1;
  }

  return sb.toString();
}

String reverse5(String s) {
  var length = s.length;
  var charCodes = new List(length);
  for(var index = 0; index < length; index++) {
    charCodes[index] = s.codeUnitAt(length - index - 1);
  }

  return new String.fromCharCodes(charCodes);
}
main() {
  var s = "Lorem Ipsum is simply dummy text of the printing and typesetting industry.";

  time('reverse0', () => reverse0(s));
  time('reverse1', () => reverse1(s));
  time('reverse2', () => reverse2(s));
  time('reverse3', () => reverse3(s));
  time('reverse4', () => reverse4(s));
  time('reverse5', () => reverse5(s));
}

Here is the result:

reverse0: => 331,394 ops/sec (3 us) stdev(0.01363)
reverse1: => 346,822 ops/sec (3 us) stdev(0.00885)
reverse2: => 490,821 ops/sec (2 us) stdev(0.0338)
reverse3: => 873,636 ops/sec (1 us) stdev(0.03972)
reverse4: => 893,953 ops/sec (1 us) stdev(0.04089)
reverse5: => 2,624,282 ops/sec (0 us) stdev(0.11828)