how to array list to tree in javascript?

Question

I have a list:

var list = ['parent-element', 'child-of-previus-element-1', 'child-of-previus-element-2'];

where each next element in the array is a child of the previous.

I want to transform this list into a tree structure, e.g.:

{
    "parent-element": {
        "childrens": [{
            "child-of-previus-element-1": {
                "childrens": [{
                    "child-of-previus-element-2": {
                        "childrens": []
                    }
                }]
            }
        }]
    }
}

I have tried:

var list = ['parent-element', 'child-of-previus-element-1', 'child-of-previus-element-2'];
var tree = {};

for (var i = 0; i < list.length; i++) {
    if( list[i-1] &&  tree[list[i-1]] ){
      tree[list[i-1]].childrens[list[i]] = {"childrens": []}; 
    } else {
      tree[list[i]] = {
        "childrens": []
      };
    }
}

console.log( JSON.stringify(tree) );

but the output is:

{
    "parent-element":{
        "childrens":[]
     },
     "child-of-previus-element-2":{
        "childrens":[]
     }
}

That "treelike structure" is invalid.

Jonas Wilms
– Jonas Wilms

2018-07-25 13:22:15 +00:00
Commented Jul 25, 2018 at 13:22 — Jonas Wilms
– Jonas Wilms, Commented Jul 25, 2018 at 13:22
sorry, fixed...

ar099968
– ar099968

2018-07-25 13:25:57 +00:00
Commented Jul 25, 2018 at 13:25 — ar099968
– ar099968, Commented Jul 25, 2018 at 13:25

Jonas Wilms · Accepted Answer · 2018-07-25 13:37:00Z

3

You might reduce it right:

var list = ['parent-element', 'child-of-previus-element-1', 'child-of-previus-element-2'];

var tree = list.reduceRight((child, key) => ({ [key]: { children: [child] } }), null);

console.log(JSON.stringify(tree))

edited Jul 25, 2018 at 13:37

answered Jul 25, 2018 at 13:30

Jonas Wilms

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2 Comments

Jonas Wilms Over a year ago

@ar099968 glad to help :)

FatalMerlin Over a year ago

Good solution, but downplaying other peoples problems with "too easy" feels kinda off..., no offense. (Still upvoted because you solved while I was still thinking about it :) )

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