Javascript array modification

Question

I have an array of objects that look like this:

[{year: "1920", count: 0}, {year: "1921", count: 2}, {year: "1925", count: 0}, {year: "1930", count: 21}, ....]

I want to, based on a starting year(ex. 1900) and an ending year(ex. 2000) fill up all years in between in the array with objects({year: -year-, count: 0}), so in the example above, the years between 1900 and 1920 would be added, and 1921-1925, and 1925-1930, and 1930-2000.

Has anyone had a similar problem and can help? Would be very much appreciated!

Edit: What I have tried so far is a simple for loop, checking in each iteration if the year is in the array .. But I feel like that is not a good and efficient way to solve it

• Jejun: It would be better if you let us know what you have tried so far.
• alp123: I have tried a simple for loop, checking in each iteration if the year is in the array .. But I feel like that is not a good and efficient way to solve it .. (Updated the original question) @Jejun
• Andy Ray: Add the code that you've tried and what you're having trouble with. Adding more specific example output will help as well.

Answer 1

You can first create an object from current years array and generate the new array while checking if the year present in that object:

const presentYear = [{year: "1920", count: 0}, {year: "1921", count: 2}, {year: "1925", count: 0}, {year: "1930", count: 21}];
const presentYearObj = Object.fromEntries(presentYear.map(k=>[k.year, k]));
const allData = Array.from({length:101}, (_,i)=>presentYearObj[`${1900+i}`] || ({year:`${1900+i}`, count:0}));
console.log(allData);

Answer 2

let arrs =
 [
 {year: "1920", count: 0},
 {year: "1921", count: 2},
 {year: "1925", count: 0},
 {year: "1930", count: 21}
 ]
let arr2 = arrs.map(it => {
 return +it.year
})
console.log(arr2)
for (let i = 1900; i < 2000; i++) {
 if (!arr2.includes(i)) {
 arrs.push({year: i + '', count: 0})
 }
}
console.log(arrs.length)

Answer 3

function fillYears(from, to, existingArray) {
 
 let existingObject = {};
 existingArray.map(x => existingObject[x.year] = x.count);
 
 let yearsArray = [];
 for (let i = from; i <= to; i++) {
 yearsArray.push({ 
 year: i.toString(), 
 count: existingObject[i] || 0
 });
 }
 
 return yearsArray;
 
}
let arrYears = [
 { year: "1920", count: 0},
 { year: "1921", count: 5},
 { year: "1925", count: 0},
 { year: "1930", count: 10}
 ];
arrYears = fillYears(1900, 2000, arrYears);
console.log( arrYears );

This function creates a new array, completing the count values from the existing array.