How To Create A Set In Javascript
How to create nested child objects in Javascript from array?
list = [a,b,c] array to below object form using javascript
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Edit
On a second thought, makeNestedObjWithArrayItemsAsKeys can further be simplified, and written concisely!
const makeNestedObjWithArrayItemsAsKeys = (arr) => { const reducer = (acc, item) => ({ [item]: acc }); return arr.reduceRight(reducer, {}); }; cc: dvv.avinash Ivan Rahul Sidhant Siddarthan
The Object.assign in the original function (below) is unnecessary... have noticed it thanks to Jason's answer!
It'd be amiss on my part, to not mention that Jason's solution here (as I see it) is the most elegant one of the lot!
const makeNestedObjWithArrayItemsAsKeys = (arr) => { return arr.reduceRight( (accumulator, item) => { const newAccumulator = {}; newAccumulator[item] = Object.assign( {}, accumulator ); return newAccumulator; }, {} ); }; Given the following list:
const list = ["a", "b", "c"]; ...the return value of makeNestedObjWithArrayItemsAsKeys(list) will be the following object:
{ a: { b: { c: {} } } } Hope that answers your question! :)
+2 Beers for that function name! 🙌
The less code you use, the less there is to break
Whilst it's fun to see all the complex answers, mine's a bit more draconian... you probably won't find a faster routine for doing this. It exploits that objects are always passed by reference in JavaScript, even during assignment.
function nest(arr) { for (var obj = {}, ptr = obj, i = 0, j = arr.length; i < j; i++) ptr = (ptr[arr[i]] = {}); return obj; } No recursive calls, no fancy mapping/each, no nested function calls/multiple functions, no long-winded objectAssign, no foreach or other methods that won't work in legacy browsers. Just a simple FOR loop and assignment. Should work all the way back to IE5.
Show + 2 replies
Sai Kishore Komanduri Even better, if you don't care about IE8/earlier, you can lose the () from that reducing it to just:
ptr = ptr[arr[i]] = {};
I only included the extra () to be sure it works all the way back to IE 5.x since I'm obnoxious that way.
since I'm obnoxious that way.
... plus that's your favourite browser :P
PhD candidate researching software visualisation
let list = ['a', 'b', 'c'] let root = {} let parent = null; for(let el of list) { if(parent === null) parent = nest(el, root) else { parent = nest(el, parent); } } function nest (el, parent) { let node = {} parent[el] = node; return node; } console.log(root); Output
{ a: { b: { c: {} } } } Show + 1 replies
The function nest() takes two parameters 1) el and 2) parent.
The first time nest is called we pass a (first element of the array) and root to the function.
Nest() creates a new object called node. Node then gets added to the parent parameter. Parent corresponds to root the first time the function is called. Then node is returned.
A reference of node is actually returned and not a copy (THIS IS IMPORTANT). Therefore, when nest() gets called a second time the parent parameter is actually a reference to the first node object that was created in the previously called nest() function.
Hi Ivan,
Your approach looks working. I have a doubt.
I wanted the output to be: { a: { b: { c: [{d:e,f:h} } } }
I modified the function nest where if el is equal to c, then add [] instead of {}. After that I cannot achieve adding key,value pairs inside the array [].
If I use root to add KVP, its adding like "{c:[],{d:e,...}} (where I need the d,e inside the array)
Can you guide me here?
Web developer from London
IMHO this question is too abstract to be of any transferrable value - you haven't said why you want to do this, though I suspect your example is simply too generic.
I'm not saying there isn't any value in such a reduction algorithm; it's just meaningless without context – anyone who answers has no guarantee they'll be providing something of practical use.
- Where is the data coming from?
- What value should be in the final nested result?
- Will the structure already exist?
- Can it take an input value?
- Will it done by machines or humans?
- Etc...
If all these are requirements, I suggest looking at Lodash set() :
- https://lodash.com/docs/4.17.4#set
Sets the value at
pathofobject. If a portion ofpathdoesn't exist, it's created. Arrays are created for missing index properties while objects are created for all other missing properties. Use_.setWithto customizepathcreation.
As a programming exercise, my take on it is:
function set(keys, value, obj) { obj = obj || {} keys = typeof keys === 'string' ? keys.match(/\w+/g) : Array.prototype.slice.apply(keys) keys.reduce(function(obj, key, index) { obj[key] = index === keys.length - 1 ? value : typeof obj[key] === 'object' && obj !== null ? obj[key] : {} return obj[key] }, obj) return obj } // new object var obj = set(['a', 'b', 'c'], 1) // { a: { b: { c: 1 } } } // existing objects set(['b', 'c'], 2, obj) // { a: { b: { c: 1 } }, b: { c: 2 } } // new props set(['x', 'y'], 3, obj.b) // { a: { b: { c: 1 } }, b: { c: 2, x: { y: 3 } } } // existing props set(['x', 'z'], 4, obj.b) // { a: { b: { c: 1 } }, b: { c: 2, x: { y: 3, z: 4 } } } // keys as string set('x y z', 5, obj) // { a: { b: { c: 1 } }, b: { c: 2, x: { y: 3, z: 4 } }, x: { y: { z: 5 } } } obj In general programming terms, usability and practicality is more valuable than brevity or speed.
Show + 1 replies
That question wouldn't survive on StackOverflow! But I guess this isn't SO :P
var list = ['a', 'b', 'c']; var root = {}; list.forEach((item) => { var current = {}; current[item] = {}; var keys = Object.keys(current); var t = findRoot(root); t[keys[0]] = current[keys[0]]; }); function findRoot (obj) { var keys = Object.keys(obj); if (keys.length == 0) return obj; var lastKey = keys[keys.length - 1]; return obj[lastKey]; } console.log(root);
var name = ["a","b","c","d"] var index = {} var root = index for( var i=0;i<name.length;i++){ var char = name[i]; root[char] = {} root = root[char] // on next iteration context will be // newly created object } console.log(index); How To Create A Set In Javascript
Source: https://hashnode.com/post/how-to-create-nested-child-objects-in-javascript-from-array-cj9tsc3we01m0uowu4pyuesy0
Posted by: nivensonst1959.blogspot.com
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