Create new array of objects based on two arrays in Javascript

Question

I want to get the array of objects created from two simple arrays:

const array1 = [20, 2, 35, 86]
const array2 = [8, 86, 15, 23, 35, 44]

The expected result:

const result = [
 { id: 20, value: false },
 { id: 2, value: false },
 { id: 35, value: true },
 { id: 86, value: true },
];

The array1 length is the one that matters. So I need to find matched values in both arrays as showed in the expected result.

Thank you very much for your help.

• pbachman: what have you tried so far ? can you show us your current code ?
• C3roe: Please go read How to Ask. You are supposed to show us what you tried, and explain what the specific problem with it was. This is not a code-writing service.

Answer 1

You can combine map with includes:

array1.map(i => ({id: i, value: array2.includes(i)}))

• omer: Neat solution! I think it's worth mentioning that for large arrays it'd be better to use sets for better performance

Answer 2

Should be simple. Loop through the first array using Array.map & return an object.

const array1 = [20, 2, 35, 86]
const array2 = [8, 86, 15, 23, 35, 44]
const result = array1.map(i => ({ id: i, value: array2.includes(i) }))
console.log(result)

Answer 3

Create a set from the second array:

const a2set = new Set(array2);

then map your first array:

array1.map(v1 => ({id:v1, value: a2set.has(v1)}))

Answer 4

Start a loop against first array and check if that element exists in second array or not.

If element exists push it to array containing objects with flag true or else as false.

const array1 = [20, 2, 35, 86]
const array2 = [8, 86, 15, 23, 35, 44]
var objArray = []
array1.forEach(function(elem){
 objArray.push({
 id : elem,
 value : array2.indexOf(elem) != -1 ? true : false
 });
});
console.log(objArray);

Answer 5

You can use array indexOf to find if the item is inside the second array.

const array1 = [20, 2, 35, 86];
const array2 = [8, 86, 15, 23, 35, 44];
let output = [];
array1.forEach((number) => {
 output.push({
 id: number,
 value: array2.indexOf(number) !== -1
 });
});
console.log(output);

Answer 6

Try a simple for loop:

 
const array1 = [20, 2, 35, 86];
const array2 = [8, 86, 15, 23, 35, 44];
var res = [];
for (var i = 0; i < array1.length; i++) {
 if (array2.includes(array1[i])) {
 res.push({ id: array1[i], value: true });
 } else {
 res.push({ id: array1[i], value: false });
 }
}
console.log(res);

Answer 7

Try the following. If performance is important, or if the arrays might include a large amount of elements, I'd consider using sets for better lookup performance.

const array1 = [20, 2, 35, 86]
const array2 = [8, 86, 15, 23, 35, 44]
const result = array1.map(element => {
 return {
 id: element,
 value: array2.includes(element)
 };
})