How to reformat json as nested json by parent_id

Question

Here is the Json array, Every object has is_parent and parent_id properties, If and object has children objects then it's is_parent property is 1 and vice versa.

let list = [
    {id: 4, name: 'dd', is_parent: 1, parent_id: 0},
    /**/{id: 5, name: 'ee', is_parent: 0, parent_id: 4},
    /**/{id: 6, name: 'ff', is_parent: 1, parent_id: 5},
    /**//**/{id: 7, name: 'gg', is_parent: 0, parent_id: 6},

    {id: 8, name: 'hh', is_parent: 1, parent_id: 0},
    /**/{id: 9, name: 'ii', is_parent: 0, parent_id: 8},

    {id: 10, name: 'jj', is_parent: 1, parent_id: 0},
    /**/{id: 11, name: 'kk', is_parent: 1, parent_id: 10},
    /**//**/{id: 12, name: 'll', is_parent: 1, parent_id: 11},
    /**//**//**/{id: 13, name: 'mm', is_parent: 0, parent_id: 12},
],

I want to format above json array as below

let array = [
    {
        id: 4,
        name: 'dd',
        is_parent: 1,
        parent_id: 0,
        children: [
            {id: 5, name: 'ee', is_parent: 0, parent_id: 4},
            {
                id: 6,
                name: 'ff',
                is_parent: 1,
                parent_id: 5,
                children: [
                    {id: 7, name: 'gg', is_parent: 0, parent_id: 6}
                ]
            }
        ]
    },

    {
        id: 8,
        name: 'hh',
        is_parent: 1,
        parent_id: 0,
        children: [
            {id: 9, name: 'ii', is_parent: 0, parent_id: 8}
        ]
    },

    {
        id: 10,
        name: 'jj',
        is_parent: 1,
        parent_id: 0,
        children: [
            {
                id: 11,
                name: 'kk',
                is_parent: 1,
                parent_id: 10,
                children: [
                    {
                        id: 12,
                        name: 'll',
                        is_parent: 1,
                        parent_id: 11,
                        children: [
                            {id: 13, name: 'mm', is_parent: 0, parent_id: 12}
                        ]
                    }
                ]
            }
        ]
    },
]

I tried to do this by foreach loop inside another foreach loop but it didn't work

Answer 1

'use strict';
const createDataTree = dataset => {
    const hashTable = Object.create(null);
    dataset.forEach(aData => hashTable[aData.id] = {...aData, children: []});
    const dataTree = [];
    dataset.forEach(aData => {
        if(aData.parent_id) {
            hashTable[aData.parent_id].children.push(hashTable[aData.id]);
        }
        else {
            dataTree.push(hashTable[aData.id]);
        }
    });
    console.log(JSON.stringify(dataTree, null ,4))
    return dataTree;
};

const list = [
        {id: 4, name: 'dd', is_parent: 1, parent_id: 0},
        /**/{id: 5, name: 'ee', is_parent: 0, parent_id: 4},
        /**/{id: 6, name: 'ff', is_parent: 1, parent_id: 5},
        /**//**/{id: 7, name: 'gg', is_parent: 0, parent_id: 6},

        {id: 8, name: 'hh', is_parent: 1, parent_id: 0},
        /**/{id: 9, name: 'ii', is_parent: 0, parent_id: 8},

        {id: 10, name: 'jj', is_parent: 1, parent_id: 0},
        /**/{id: 11, name: 'kk', is_parent: 1, parent_id: 10},
        /**//**/{id: 12, name: 'll', is_parent: 1, parent_id: 11},
        /**//**//**/{id: 13, name: 'mm', is_parent: 0, parent_id: 12},
    ];
createDataTree(list);

I have modifed the code and taken example from here . This is really good example and works like a charm