To insert missing element from one array to another object array

Question

The first array is something like this

arrayA = [{x:"abc",y:2},{x:"cde",y:3},{x:"xyz",y:2}]

The second array is

arrayB = ["abc","cde","efg","ghi","xyz"]

I want to insert the element of arrayB as key-value pair which is missing in arrayA as key is the element from arrayB and value will be 0 I want the resultant arrayResult something like this

arrayResult = [{x:"abc",y:2},{x:"cde",y:3},{x:"efg",y:0},{x:"ghi",y:0},{x:"xyz",y:2}]

I tried this but didn't get the required result

for (let i = 0; i < arrayB.length; i++) {
 for (let j = 0; j <arrayA.length; j++) {
  if(arrayB[i] !== arrayA[j].x) {
   arrayA.push({x:arrayB[i],y:0})
   }
 }
}

I am new to js. can anyone help me with this?

Nina Scholz · Accepted Answer · 2021-03-17 18:18:19Z

1

You could take a closure over an index of arrayA and check the value of arrayB is equal of the first array, then return that object, otherwise create a new object and return this by iterating the second array.

const
    arrayA = [{ x: "abc", y: 2 }, { x: "cde", y: 3 }, { x: "xyz", y: 2 }],
    arrayB = ["abc", "cde", "efg", "ghi", "xyz"],
    result = arrayB.map((i => x => arrayA[i].x === x
        ? arrayA[i++]
        : { x, y: 0 }
    )(0));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Mar 17, 2021 at 18:18

Nina Scholz

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Comments

Felipe Chernicharo · Accepted Answer · 2021-03-17 18:27:46Z

0

You can use Array.reduce for this job:

let arrayA = [{x:'abc', y:2}, {x:'cde', y: 3}, {x:'xyz', y:2}]
let arrayB = ['abc', 'cde', 'efg', 'ghi', 'xyz']

Here goes the solution:

const result = arrayB.reduce((acc, str) => {

  const found = arrayA.find(item => item.x === str)

    if(found) {
       acc.push(found) 
    } else{
      acc.push({x:str, y:0})
    }

    return acc
},[])

The result should be what you want 🤙🏽

console.log(result) => // [{x:"abc",y:2},{x:"cde",y:3},{x:"efg",y:0},{x:"ghi",y:0},{x:"xyz",y:2}]

With the reduce method you can iterate over arrayB and for each of its items, check if there's an object in arrayA whose property x match the item.

Case yes, just push it up to the result array.

Case no, create a new object { x: < arrayB item >, y: 0 }

edited Mar 17, 2021 at 18:27

answered Mar 17, 2021 at 18:20

Felipe Chernicharo

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Comments

Siva Kondapi Venkata · Accepted Answer · 2021-03-18 06:56:07Z

0

preprocess and build a lookup object based on key x and use map on arrayB.

arrayA = [
  { x: "abc", y: 2 },
  { x: "cde", y: 3 },
  { x: "xyz", y: 2 },
];

arrayB = ["abc", "cde", "efg", "ghi", "xyz"];

const lookupA = arrayA.reduce((acc, curr) => ({ ...acc, [curr.x]: curr }), {});
const result = arrayB.map((x) => lookupA[x] ?? { x, y: 0 });

console.log(result)

answered Mar 18, 2021 at 6:56

Siva Kondapi Venkata

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