The Daily WTF: Curious Perversions in Information Technology

Dragnslcr · 2026-02-18 Reply Edit Admin

Also, little pro-tip for generating comma separated code, and this is just a real tiny optimization: before the loop append item zero, start the loop with item 1, and then you can unconditionally prepend a comma, removing any conditional logic from your loop.

Or if you're using a sane language, use the builtin join function.

Steve_The_Cynic · 2026-02-18 Reply Edit Admin

Or if you're using a sane language, use the builtin join function.

Above all, this!

Addendum 2026-02-18 07:36: And, curiously, despite all its many insanities, JS is sufficiently sane in this particular respect. Well, unless I've missed something about Array.prototype.join()

2026-02-18 Reply Admin

I have seen a lot of code where they always append the separator comma, and after the loop they take a substring of the result with all characters except the last. What they usually forget is the case when the array is empty and the for-loop is skipped. There it always crashes badly when taking the substring.

Another way of doing it:

let arrayString = '{';
let separator = "";
  for(let i = 0; i < jsArray.length; i++) {
    arrayString += separator + jsArray[i];
    separator=",";
    }
  }
  arrayString += '}';

2026-02-18 Reply Admin

oh well, the newline did not work. And I can't correct my pevious post... Trying with two slashes instead of backslashes ... Another way of doing it: // let arrayString = '{'; // let separator = "";// for(let i = 0; i < jsArray.length; i++) { // arrayString += separator + jsArray[i];// separator=",";// }// arrayString += '}';//

dpm · 2026-02-18 Reply Edit Admin

separator=",";

Yeah, that's how I do it.

dpm · 2026-02-18 Reply Edit Admin

''' use three single quotes the line breaks will work for you it's also monospaced

Addendum 2026-02-18 09:05: Well, that was wrong

dpm · 2026-02-18 Reply Edit Admin

typing three backquotes
the line breaks will work for you
it's also monospaced

gordonfish · 2026-02-18 Reply Edit Admin

You could also use a ternary:

let arrayString = '{';
for(let i = 0; i < jsArray.length; i++) {
  arrayString += (i ? ',' : '') + jsArray[i];
}
arrayString += '}';

But as @Dragnslcr said, join() is the better way, and as @Steve_The_Cynic mentioned, JavaScript has it built-in:

let arrayString = '{' + jsArray.join(',') + '}';

Dragnslcr · 2026-02-18 Reply Edit Admin

I'll also post the periodic reminder that the comments here now render Markdown, so you can use that for quotes, code, etc.

Contains Some Bad Choices

Leave a comment on “Contains Some Bad Choices”