Loop through array to add keys to every nth element

February 9, 2024

I have an array

    super = ["Month 1","22 - Feb - 2024","29 - Feb - 2024","7 - Mar - 2024",  "Month 2","23 - Mar - 2024","30 - Mar - 2024","6 - Apr - 2024"].

I’d like to add the following keys to every 4 elements:

    keys=["tp","early","target","late"]

My final array would look like

    final=[tp:"Month 1",early:"22 - Feb - 2024",target:"29 - Feb - 2024",late:"7 - Mar - 2024", tp:"Month 2",early:"23 - Mar - 2024",target:"30 - Mar - 2024",late:"6 - Apr - 2024"]

.map() might be an option, but I’m not sure how to loop for every 4th element and I’m also not real familiar that. I think something like for (var i = 0; i < super.length; i += 4) {stuff} would work, but not sure what to do in the ‘stuff’ portion.

>Solution :

This will give you your desired output.

super.map((s, i) => ({[keys[i%4]]: s}))

Small breakdown:

super.map((s, i) => {
  //we used remainder operator[1] here.
  const correctKey = keys[i % 4];
  //this is the syntax used for assigning object key from string value.
  return { [correctKey]: s };
});

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Remainder