Javascript create Object by array

Question

I try to create an object with a value for the last key. I just have an Array with the keys and the value but dont know how it will be possible to create an object without use references in javascript.

As far as I know there isnt a way to create a reference of a variable in javascript.

This is what i have:

var value = 'test';
var keys = ['this', 'is', 'a', 'test'];

This is what i want:

myObject: {
   this : {
     is: {
       a : {
         test : 'test'
       }
     }
   }
}

Any idea how i can do this the best way in JavaScript ?

I dont think that JSON can help me with this. I have an Array with Keys. Every key have to be a new object in the object. And the last key has the value of the variable "value". — TJR
– TJR, Commented Jan 8, 2014 at 5:20
Are you sure that inner value isn't meant to be test: 'Test'? — Phil
– Phil, Commented Jan 8, 2014 at 5:31
@Phil yes - for sure. My fault. I will edit the question. But thanks to your awesome answer (: It still works how it has to work. — TJR
– TJR, Commented Jan 8, 2014 at 5:47
I edited to a salomonic data, so no previously correct answer gets incorrect :) — Edgar Villegas Alvarado
– Edgar Villegas Alvarado, Commented Jan 8, 2014 at 5:55

Phil · Accepted Answer · 2017-03-09 04:33:09Z

10

How about this...

const value = 'test'
const keys = ['this', 'is', 'a', 'test']

const myObject = keys.reduceRight((p, c) => ({ [c]: p }), value)

console.info(myObject)

Or, if you're not a fan of object literal key shortcuts and arrow functions...

keys.reduceRight(function(p, c) {
  var o = {};
  o[c] = p;
  return o;
}, value);

See Array.prototype.reduceRight() - Polyfill if you need IE <= 8 support.

edited Mar 9, 2017 at 4:33

answered Jan 8, 2014 at 5:27

Phil

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4 Comments

Edgar Villegas Alvarado Over a year ago

It has an error in the final node, but this code is so beautiful I can't downvote it

Edgar Villegas Alvarado Over a year ago

It finally creates test: "Test" instead of Test : "test". But anyway, altough it's not correct it has my vote, nice code

Phil Over a year ago

@EdgarVillegasAlvarado Ah. The OP's description makes it sound like the value should be the inner-most value, not key. I've asked for clarification

TJR Over a year ago

Wow. Awesome. Never heard about this method in javascript before. Thanks for this clean code. I will try it and will work with this. Edit: I tried it and this works fine for my issue! Many thanks dude :)

Edgar Villegas Alvarado · Accepted Answer · 2014-01-08 05:52:25Z

4

With this:

var curObj = myObject = {};
for(var i=0; i<keys.length-1; i++)
   curObj = curObj[keys[i]] = {};    
curObj[value] = keys[i];

Outputs:

{
   this : {
     is: {
       a : {
         Test : 'test'
       }
     }
   }
}

As opposed to the other answers, this outputs exactly what you asked for.

Cheers

edited Jan 8, 2014 at 5:52

answered Jan 8, 2014 at 5:27

Edgar Villegas Alvarado

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6 Comments

Phrogz Over a year ago

Did you get that terseness from my answer, or on your own? (s'ok either way)

Edgar Villegas Alvarado Over a year ago

I was refactoring each minute (you can see the editions), didn't even realize you answered. Mine gives a different result, though

Phrogz Over a year ago

Yes, yours gives the answer the OP asks for (which I suspect is wrong :)

Phrogz Over a year ago

Anyhow, note that the value of i after the loop will be the value of keys.length-1, so you can use that to make your last line cleaner, if you like.

Phil Over a year ago

Don't look now but OP updated their question ;). Still gets my upvote for the effort of figuring out how to solve the more difficult original query

|

Phrogz · Accepted Answer · 2014-01-08 05:33:14Z

2

var o={}, c=o;
var value = 'Test';
var keys = 'this is a test'.split(' ');

for (var i=0; i<keys.length-1; ++i) c = c[keys[i]] = {};
c[keys[i]] = value;

console.log(JSON.stringify(o));
// {"this":{"is":{"a":{"test":"Test"}}}}

answered Jan 8, 2014 at 5:33

Phrogz

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2 Comments

Phil Over a year ago

keys was already an array? Why turn it into a string then back to an array?

Phrogz Over a year ago

@Phil BC I was too lazy to use the mouse to copy/paste, and I wanted to show the OP an alternate lazy-programmer way to create an array of strings with less typing.

adhil muhammed · Accepted Answer · 2021-04-10 01:25:23Z

0

If you want the output like

{
   this : {
     is: {
       a : 'test'
     }
   }
}

Do the following

var keys = ['this', 'is', 'a', 'test'];
var output = keys.reduceRight((p,c)=>({[c]:p}))
console.log(output)

And the output will be like

{ this: { is: { a: 'test' } } }

answered Apr 10, 2021 at 1:25

adhil muhammed

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