JS filter array on key

Question

So an example could be:

let a = [10,20,30,40,50,60,70,80];
let b = [1,2,6];
console.log([a[1], a[2], a[6]);

which an explanation can be something like: get the objects of a which index is in b .

I know that i can do something like

const f = (a, b) => {
    let result = [];
    b.forEach(element => {
        result.push(a[element]);
    });
    return result;
}

But maybe there is a more concise way

EDIT: so far the best i can get is this

a.filter((n, index)=>b.includes(index)));

but is not the same, infact if b = [0,0,0] it does not returns [a[0],a[0],a[0]] but [a[0]]

Answer 1

Iterate array b with Array.map() and return the value at the respective index from array a :

 const a = [10,20,30,40,50,60,70,80]; const b = [1,2,6]; const result = b.map(index => a[index]); console.log(result);

Answer 2

The .from method of the global Array object lets you transform an array into a new array in a manner similar to .map() .

 let a = [10,20,30,40,50,60,70,80]; let b = [1,2,6]; let result = Array.from(b, n => a[n]); console.log(result);

Because you want to convert b from indexes into values with a 1 to 1 relationship, some sort of "mapping" operation is what you're generally after.

Answer 3

Another way could be:

 var out = []; for(let x of b){ out.push(a[x]); }