String concatenation performance

Benchmark created on

Preparation HTML

<script>
  var a = 'a b c d e f g';
  function generateArr(i) {
    var arr = [];
    while (i--) {
      arr.push(a);
    }
    return arr;
  }
  
  var smallArr = generateArr(50),
  mediumArr = generateArr(1000),
  largeArr = generateArr(10000);
</script>

Test runner

Ready to run.

Testing in
TestOps/sec
small loop with join
var str = smallArr.join('');
ready
small loop without join
var str = '',
    arr = smallArr.join('');
for (var i = 0, len = arr.length; i < len; i++) {
  str += arr[i];
}
ready
medium loop with join
var str = mediumArr.join('');
ready
medium loop without join
var str = '',
    arr = mediumArr.join('');
for (var i = 0, len = arr.length; i < len; i++) {
  str += arr[i];
}
ready
large loop with join
var str = largeArr.join('');
ready
large loop without join
var str = '',
    arr = largeArr.join('');
for (var i = 0, len = arr.length; i < len; i++) {
  str += arr[i];
}
ready
small loop with operator
var str = '';
for (var i = 0, len = 50; i < len; i++) {
  str += a;
}
ready
medium loop with operator
var str = '';
for (var i = 0, len = 1000; i < len; i++) {
  str += a;
}
ready
large loop with operator
var str = '';
for (var i = 0, len = 10000; i < len; i++) {
  str += a;
}
ready

Revisions

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