How to create array of object from two different length of array javascript

Question

How to create array of object from two different length of array

for example

arr1 = ["first","second","third","fourth","fifth","Sixth"]
arr2 = [["1","2","3","4","5","6"],["7","8","9","10","11","12"],["1","2","3","4"]]

finalArray = [{
   first:1,
   second:2
   third:3,
   fourth:4,
   fifth:5,
   sixth:6
},{
   first:7,
   second:8
   third:9,
   fourth:10,
   fifth:11,
   sixth:12
}]

I tried this using map but getting every key value pair as whole object

example

[
 {first: 1}
 {second: 2}
 {third: 3}
 {fourth: 4}
]

Robby Cornelissen · Accepted Answer · 2021-10-28 06:59:46Z

4

With map() and reduce():

const arr1 = ["first", "second", "third", "fourth", "fifth", "Sixth"];
const arr2 = [["1", "2", "3", "4", "5", "6"],
              ["7", "8", "9", "10", "11", "12"],
              ["1", "2", "3", "4"]];

const res = arr2.map(v => v.reduce((a, v, i) => ({...a, [arr1[i]]: v}), {}));

console.log(res);

answered Oct 28, 2021 at 6:59

Robby Cornelissen

98.6k23 gold badges154 silver badges180 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Dai Over a year ago

I feel this is a bad approach because it has poor runtime complexity: you're using the spread-operator (which will perform an O(n) array copy on every input element) in reduce.

Robby Cornelissen Over a year ago

@Dai You are correct, but for small data volumes the difference will be negligible, and if we were aiming for optimal runtime performance, we would not be using any of the array functions like map() or reduce() anyway. Another thing worth mentioning is that we don't know what optimizations the JavaScript engine introduces, so it's hard to determine actual runtime complexity. With no stipulations about performance requirements in the question, I err on the side of conciseness and readability.

sahil555 Over a year ago

So what could be the best approach beside any predefined function @RobbyCornelissen

Robby Cornelissen Over a year ago

Iterate using only for loops, regular property assignments to objects, push to add to array.

Yves Kipondo · Accepted Answer · 2021-10-28 07:05:29Z

0

You can take advantage of Array.prototype.reduce to update the shape of the result array

let arr1 = ["first","second","third","fourth","fifth","Sixth"];
let arr2 = [["1","2","3","4","5","6"],["7","8","9","10","11","12"],["1","2","3","4"]];

let result = arr2.reduce((accumulator, current) => {
  let obj = arr1.reduce((acc, currentKey, index) => {
    if(current.indexOf(index) && current[index] !== undefined ){
      acc[[currentKey]] = current[index];
    }
    return acc;
  }, {});
  return accumulator.concat(obj);
}, []);

console.log(result);

answered Oct 28, 2021 at 7:05

Yves Kipondo

5,6931 gold badge22 silver badges33 bronze badges

Comments

elbik · Accepted Answer · 2021-10-28 07:56:38Z

0

without reduce() and covered edge case when the arr1 contains fewer elements as the element from arr2

const arr1 = ["first","second","third","fourth","fifth","Sixth"]
const arr2 = [["1","2","3","4","5","6"],["7","8","9","10","11","12"],["1","2","3","4"]]

const res = arr2.map(values => {
    const res = {}
    for(const [index, value] of arr1.entries()){
        if(values[index]) {
            res[value] = values[index] // or parseInt(values[index])
        } else {
            break
        }
    }
    return res
})

console.dir(res)

answered Oct 28, 2021 at 7:56

elbik

1,9372 gold badges18 silver badges21 bronze badges

1 Comment

Dai Over a year ago

if(values[index]) { - there's a bug here: if the values[index] value is falsy (e.g. 0) then your for loop will break too early.

Collectives™ on Stack Overflow

How to create array of object from two different length of array javascript

3 Answers 3

4 Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related