convert JSON object to JSON tree

Question

var obj = [{
    id: 1,
    child:[2,4],
    data : \"hello\"
},{
    id: 2,
    child:[3],
    data : \"I m second\"
},
{   
    id: 3,
    child:[],
    data : \"I         


        

Answer 1

A proposal with a temporary object for keeping the reference to the items.

var array = [{ id: 1, child: [2, 4], data: "hello" }, { id: 2, child: [3], data: "I m second" }, { id: 3, child: [], data: "I m third" }, { id: 4, child: [6], data: "I m fourth" }, { id: 5, child: [], data: "I m fifth" }, { id: 6, child: [], data: "I m sixth" }],
    tree = [];

array.forEach(function (a) {
    if (!this[a.id]) {
        this[a.id] = { id: a.id };
        tree.push(this[a.id]);
    }
    this[a.id].data = a.data;
    this[a.id].child = a.child.map(function (b) {
        this[b] = this[b] || { id: b };
        return this[b];
    }, this);
}, Object.create(null));

document.write('
' + JSON.stringify(tree, 0, 4) + '
');