Create nested Javascript Object dynamically

Question

I have got a . (dot) separated string, from which I want to create nested JSON object. The length of the string is not fixed. For example,

var string = 'a.b.c.d';

Then my JSON object should be as following:

a: {
 b: {
 c:{
 d: {
 //Some properties here. 
 }
 } 
 }
}

I've tried following code:

var packageName = "a.b.c.d"
var splitted = packageName.split('.');
var json = {};
for(var i=0;i<splitted.length-1;i++){
 json[splitted[i]] = splitted[i+1];
}

But this returns

{
 a: 'b', 
 b: 'c',
 c: 'd'
}

But this is not what I want. I've also searched on google and found similar questions, but no solutions answer my problem. For example this.

• user9366559: You're asking how to create a nested JS object, not JSON. To create JSON would be to create your JS object, and then serialize it to the JSON text format.

Answer 1

A good use case for reduce

packageName = "a.b.c.d";
initProps = {hi: 'there'};
obj = packageName.split('.').reduceRight((o, x) => ({[x]: o}), initProps);
console.log(JSON.stringify(obj))

If you find loops easier to work with, a loop could be written concisely as

result = {};
ptr = result;
for (let prop of packageName.split('.'))
 ptr = ptr[prop] = {};

• Kaushal28: Thanks for alternative. But it's quite difficult for me to understand this. +1.
• user9366559: Excellent use case for reduce[Right]. So many nasty and incomprehensible examples of functional programming get posted here, especially with reduce, it's nice to see clean, clear, idiomatic examples.

Answer 2

You need to create a new object each time and attribute it to the last object created. And it goes until splitted.length, not splitted.length - 1, because you're using <, not <=.

var packageName = "a.b.c.d";
var splitted = packageName.split('.');
var json = {};
var current = json;
for (var i = 0; i < splitted.length; i++) {
 current[splitted[i]] = {};
 current = current[splitted[i]];
}
console.log(json);

• Kaushal28: correct! I didn't just think of this simple logic. Thanks . +1 and accept!

Answer 3

You may use the last splittted part as property for some payload.

I suggest to keep the object reference and use a temporary variable for aceessing an creating a new property, if necessary.

Please avoid the use of JSON for not stringified objects.

var packageName = "a.b.c.d",
 splitted = packageName.split('.'),
 result = {},
 temp = result,
 i;
 
for (i = 0; i < splitted.length - 1; i++) {
 temp[splitted[i]] = temp[splitted[i]] || {};
 temp = temp[splitted[i]];
}
temp[splitted[i]] = { some: 'data' };
console.log(result);