How can I get a key in a JavaScript 'Map' by its value?

Question

I have a JavaScript 'Map' like this one

let people = new Map(); people.set('1', 'jhon'); people.set('2', 'jasmein'); people.set('3', 'abdo'); 

I want some method to return a key by its value.

let jhonKey = people.getKey('jhon'); // jhonKey should be '1' 

Answer 1

You can use a for..of loop to loop directly over the map.entries and get the keys.

function getByValue(map, searchValue) {   for (let [key, value] of map.entries()) {     if (value === searchValue)       return key;   } }  let people = new Map(); people.set('1', 'jhon'); people.set('2', 'jasmein'); people.set('3', 'abdo');  console.log(getByValue(people, 'jhon')) console.log(getByValue(people, 'abdo'))

Answer 2

You could convert it to an array of entries (using [...people.entries()]) and search for it within that array.

let people = new Map(); people.set('1', 'jhon'); people.set('2', 'jasmein'); people.set('3', 'abdo');      let jhonKeys = [...people.entries()]         .filter(({ 1: v }) => v === 'jhon')         .map(([k]) => k);  console.log(jhonKeys); // if empty, no key found otherwise all found keys.