Get value from nested array

Question

i have an array that represents position inside nested array

const level = [2,1,0];

and nested array

const array = [

    [1,2,3,4],
    [22,33,444],
    [[7],[8],[9]]
    ];

i want to get element which position is represented in a level array, manually i would get it this way:

array[2][1][0]

but i need to write a function that itterates over level array which can be any length and returns element from this position, i've tried to use es6 reduce for this purpose but didn't succed can some1 help me with this issue, what am i doing wrong?

level.reduce((prev,curr) => {
  return prev[curr];
}, level[0]);

desired result: for level = [0,0] get value 1 for level = [2,1,0] get value 8

You starting value should probably be `array`, not `level[0]`, right? Since that's what you're starting from and narrowing down? — DemiPixel, Oct 07 '21 at 18:32

Guerric P · Accepted Answer · 2021-10-07T18:58:47.037

You can do that by using destructuring assignment and recursion:

const level = [2, 1, 0];

const array = [
  [1, 2, 3, 4],
  [22, 33, 444],
  [[7], [8], [9]],
];

const find = ([index, ...rest], { [index]: value }) =>
  rest.length ? find(rest, value) : value;

const result = find(level, array);

console.log(result);

Note that also works with composite trees with objects and arrays:

const level = ['prop', 1, 'otherProp', 1];

const tree = {
  prop: [
    {},
    { otherProp: [2, 4, 6] }
  ]
};

const find = ([index, ...rest], { [index]: value }) =>
  rest.length ? find(rest, value) : value;

const result = find(level, tree);

console.log(result);

Get value from nested array

1 Answers1