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Run results for: JS String '+' same v.s. different strings 2

Is there a difference in performance over many iterations of string concatenation if the string being added is the same or different each time?

Go to the benchmark
Run details:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/109.0
Firefox 109
Mac OS X 10.15
Desktop
one year ago
Test name Executions per second
Same string added each loop 355105.4 Ops/sec
Different string added each loop 9863.4 Ops/sec
Script Preparation code:
AخA
 
var nLoops = 1000;
Tests:

  • Same string added each loop

    ​x
     
    var fragmentToAdd = Math.random();
    var str = '';
    ​
    for (var i = 0; i < nLoops; i++) {
      // Just to equalize the work done in each test
      var randomString = String(Math.random());
      str += fragmentToAdd; 
    }

  • Different string added each loop

     
    var str = '';
    ​
    for (var i = 0; i < nLoops; i++) {
      var randomString = String(Math.random());
      str += randomString;
    }