How to set nested object with dynamic keys on javascript

Question

let foo = {};

const key1 = 'a';
const key2 = 'b';
const key3 = 'c';

foo[key1][key2][key3] = [1, 2];

When I trying to do something similar I get:

Uncaught TypeError: Cannot read property 'b' of undefined

Answer 1

You have to create the nested object before you can create a property in it.

let foo = {}

const key1 = 'a'
const key2 = 'b'
const key3 = 'c'

foo[key1] = {};
foo[key1][key2] = {};
foo[key1][key2][key3] = [1, 2];
console.log(foo);

If the list of keys is generated dynamically in an array, see Populate nested object from array? for a function to create all the objects.