How do I .map() a new array of values from an array and an object?

Question

let a1 = [1, 3, 5];
let a2 = {1: "a", 2: "b", 3: "c", 4: "d", 5: 2,}

// pass a function to map

const map1 = a1.map(? => ?);
console.log(map1);

// expected output: Array ["a", "c", 2]

I want the number in the array 1, 3, 5 to map to the values on the keys of a2

What should "? => ?" be for the desired result?

Edited

My question is after reading the documentation Array.prototype.map() in MDN.

My question is (not how to solve this) but to learn about the callback function in .map():

let a1 = [1, 3, 5];
let a2 = {1: "a", 2: "b", 3: "c", 4: "d", 5: 2,}

// pass a function to map

const map1 = a1.map(a2, e => a2.value);
console.log(map1);

// expected output: Array ["a", "c", 2]

Here I wanted e in a1 to match a2 and return a2 in the map function, but it's clearly wrong but after Googling for examples I guess I just had to make a question about it and try not cause too much confusion.

How much research effort is expected of Stack Overflow users before posting a Question? - Also see How do I ask a good question - Question that simple post requirements and ask for solution show no effort but expect all the free effort from others. — Nope
– Nope, Commented Dec 7, 2017 at 15:28
no its not homework, I was trying to extract the values from a JSON and I boiled it down to this question — Paul Thomas Clarke
– Paul Thomas Clarke, Commented Dec 7, 2017 at 15:33
how would you so eloquently formulate the problem where i want the values of an object mapped with an array to a new array @fran? with a poem? — Paul Thomas Clarke
– Paul Thomas Clarke, Commented Dec 7, 2017 at 15:37
Instead of asking what to do / you should show some research, too. / Otherwise it needs some luck / to analyze where you are stuck. :D — Modus Tollens
– Modus Tollens, Commented Dec 7, 2017 at 15:45

Pranav C Balan · Accepted Answer · 2017-12-07 15:25:35Z

2

Simply get the property from the object.

let a1 = [1, 3, 5];
let a2 = {1: "a", 2: "b", 3: "c", 4: "d", 5: 2,}

// pass a function to map
const map1 = a1.map(k => a2[k]);
// -----------------^^^^^^^^^^----
console.log(map1);

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