How to Add Function Returns as Key-Values in Every Object in an Array

Question

I have multiple functions that calculate values in an array of objects. I am trying to run the functions through all 7,200 objects in my array, and in turn add the return of those functions as a new Key-Value pair in each object. Below is a sample with a 5 object array instead of a 7200 object array.

I am new to JavaScript and am not sure how solve this. I can access the "Status" of each object using the const currentDay = myData.at(-1), console log the result and manually insert it as a new Key-Value Pair in the last object, change currentDay to (-2) etc. As I have 7000+ objects to do this with, I am looking for a way to not do this manually. I want my resulting new Array to look like this:

const myData2 = [
  {
    Date: "1990-02-09",
    End: "500",
    PreviousEnd: "480",
    NextEnd: "515",
    Status: ["Positive 2 Day", "Next Day Up"],
  },
  {
    Date: "1990-02-10",
    End: "515",
    PreviousEnd: "500",
    NextEnd: "505",
    Status: ["Positive 1 Day", "Next Day Down"],
  },
  {
    Date: "1990-02-11",
    End: "505",
    PreviousEnd: "515",
    NextEnd: "530",
    Status: ["Negative", "Next Day Up"],
  },
  {
    Date: "1990-02-12",
    End: "530",
    PreviousEnd: "525",
    NextEnd: "555",
    Status: ["Positive 2 Day", "Next Day Up"],
  },
  {
    Date: "1990-02-13",
    End: "555",
    PreviousEnd: "530",
    NextEnd: "570",
    Status: ["Positive 2 Day", "Next Day Up"],
  },
];

This is my current code.

 const myData = [ { Date: "1990-02-09", End: "500", PreviousEnd: "480", NextEnd: "515", }, { Date: "1990-02-10", End: "515", PreviousEnd: "500", NextEnd: "505", }, { Date: "1990-02-11", End: "505", PreviousEnd: "515", NextEnd: "530", }, { Date: "1990-02-12", End: "530", PreviousEnd: "525", NextEnd: "555", }, { Date: "1990-02-13", End: "555", PreviousEnd: "530", NextEnd: "570", }, ]; const currentDay = myData.at(-1); const endUpDown = (function () { if ( currentDay.End > currentDay.PreviousEnd && currentDay.End > currentDay.NextEnd ) { return "Positive 1 Day"; } else if ( currentDay.End > currentDay.PreviousEnd && currentDay.End < currentDay.NextEnd ) { return "Positive 2 Day"; } else { return "Negative"; } })(); const nextDayUp = (function () { if (currentDay.End < currentDay.NextEnd) { return "Next Day Up"; } else { return "Next Day Down"; } })(); const currentStatus = [endUpDown, nextDayUp]; console.log(currentStatus);

Answer 1

You have all the parts, you just need to reshuffle them to make them callable from within a map() call. All I've done is make your IIFE s into named functions with a parameter currentDay which expects an object rather than calling them on a global currentDay as in your example.

The map() call simply clones the passed object using spread syntax and then adds the status property as a tuple of your two function calls.

 const myData = [{ Date: '1990-02-09', End: '500', PreviousEnd: '480', NextEnd: '515', }, { Date: '1990-02-10', End: '515', PreviousEnd: '500', NextEnd: '505', }, { Date: '1990-02-11', End: '505', PreviousEnd: '515', NextEnd: '530', }, { Date: '1990-02-12', End: '530', PreviousEnd: '525', NextEnd: '555', }, { Date: '1990-02-13', End: '555', PreviousEnd: '530', NextEnd: '570', },]; function endUpDown(currentDay) { if ( currentDay.End > currentDay.PreviousEnd && currentDay.End > currentDay.NextEnd ) { return 'Positive 1 Day'; } else if ( currentDay.End > currentDay.PreviousEnd && currentDay.End < currentDay.NextEnd ) { return 'Positive 2 Day'; } else { return 'Negative'; } } function nextDayUp(currentDay) { if (currentDay.End < currentDay.NextEnd) { return 'Next Day Up'; } else { return 'Next Day Down'; } } const result = myData.map((currentDay) => ({...currentDay, status: [endUpDown(currentDay), nextDayUp(currentDay)], })); console.log(result);