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Bruce Axtens
Bruce Axtens

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Reversing a string using a Generator

So there's this Michiel Hendriks who says, "I'm looking for the next person to one-up this" and so here I am one-upping myself.

Here we reverse the string using a Generator to iterate backwards through the string and hand ball each character to an array that gets .join()ed at the end.

function Bruce_ReverseGenerator(string) {
  function* reverseGenerator(string) {
    let str = string;
    let index = str.length - 1;
    while (true)
      yield str.charAt(index--);

  let result = [];
  const gen = reverseGenerator(string); 
  var ch;
  while (ch = {
  return result.join("");
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Yep, decorated to run in the testing frame and giving surprisingly good results, viz:

C:\TMP> /TIMES:1000
Sarah_ForOf                 1502.905 ticks
Bruce_CharAt                2646.537 ticks
Sarah_SplitReverseJoin      2715.699 ticks
Bruce_Recursive2            2786.771 ticks
Nathanael_SplitReverseJoin  3104.762 ticks
Bruce_Recursive1            3112.511 ticks
Theophanis_SplitFor         3208.017 ticks
Sarah_Reduce                3227.539 ticks
Theophanis_SplitFor_Bruced  3706.581 ticks
Sarah_Recursive             3810.085 ticks
Bruce_ArrayApplyMap         5318.65 ticks
Bruce_ReverseGenerator      7354.585 ticks
Bruce_MapSortMap            9637.046 ticks
Bruce_CharAt2               13913.316 ticks
Bruce_RegReverse            490151.264 ticks
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