How to create a nested object given an array of keys

Question

Given is an array like this:

var level = ["a", "b", "x"];

The output should be:

{
    "a": {
        "b": {
            "x": {
            }
        }
    }
}

I tried this:

var level = ["a", "b", "x"];
var o = {};
for (var c = 0, len = level.length; c < len; c +=1 ) { 
    var part = level[c]; 
    o[part] = {}; // how to remember the last part?
}

How can I remember the last part and add the next level?

Answer 1

You can use reduceRight method by passing an arrow function as argument .

 var level = ["a", "b", "x"]; let result = level.reduceRight((obj, elem) => ({[elem]: obj}), {}); console.log(result); 

Answer 2

Simplest tweak would be to reassign o on each iteration:

 var level = ["a", "b", "x"]; var o = {}; var initialO = o; for (var c = 0, len = level.length; c < len; c +=1 ) { var part = level[c]; o[part] = {}; o = o[part]; } console.log(initialO); 

This might be a clearer way of doing it, though:

 const level = ["a", "b", "x"]; const result = {}; level.reduce((accum, key) => { accum[key] = {}; return accum[key]; }, result); console.log(result); 

Answer 3

You might use a check if the level exist and assign only an object if not set.

 function addLevels(levels, object) { levels.reduce((o, l) => o[l] = o[l] || {}, object); } var object = {}; addLevels(["a", "b", "x"], object); addLevels(["a", "d", "z"], object); console.log(object); 

Answer 4

This one, I think is easiest if you write it in a functional style.

var level = ["a", "b", "x"];
var o = {};
level.reduce(function (obj, key) {
    o[key] = {};
    return o[key];
}, o);

Answer 5

Or with a recursive function

 const level = ["a", "b", "x"]; const f = (i) => i === level.length ? {} : {[level[i]]: f(i+1)}; console.log(f(0));