Convert an array of nested objects to another nested index object

Question

I am working on one problem when I have one dynamic nested array of similar kind of objects. I have to capture the nested indexes convert it to nested object. Here is the example of two level nested array and I have written simple code to convert it to nested index object. I am looking for iterative or recursive method to handle dynamic nested array and convert to nested similar index object:-

var arr= [
 {
 "index": "1",
 "subRows": [
 {
 "index": "2",
 "subRows": undefined
 },
 {
 "index": "3",
 "subRows": undefined
 }
 ]
 },
 {
 "index": "4",
 "subRows": [
 {
 "index": "5",
 "subRows": undefined
 }
 ]
 }
];
var obj={}
for(var i =0; i<arr.length; i++) {
 obj[i]={};
 if(arr[i].subRows) {
 for(var j=0; j<arr[i].subRows.length; j++) {
 obj[i][j] = {};
 }
 }
}
console.log(obj)

• Heretic Monkey: You have no JSON in your question, and there is no such thing as a JSON Object. Just arrays and objects.
• Barmar: Seems like you probably need to write a recursive function.
• Moti Korets: Can you give an example of the result obj would look like?
• C. T.: @MotiKorets the out put will be like this, you can also run this code.0: {0:{0:{},1:{}}, 1:{0:{}}}
• amir: it will be more understandable if you add the desired output to the question

Answer 1

one simple recursive approach

var arr = [{
 "index": "1",
 "subRows": [{
 "index": "2",
 "subRows": undefined
 },
 {
 "index": "3",
 "subRows": undefined
 }
 ]
 },
 {
 "index": "4",
 "subRows": [{
 "index": "5",
 "subRows": undefined
 }]
 }
];
let obj = {
 ...arr.map(function convert(obj) {
 return { 
 ...obj.subRows?.map(convert)
 }
 })
};
console.log(obj)

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• Mulan: TIL ({ ...undefined }) is valid but [ ...undefined ] is not
• Scott Sauyet: @Thankyou: it would be convenient if [...undefined] acted like [...([])], but I think I understand why it's not done that way... a question of parametricity, one that doesn't apply in the Object case.

Answer 2

You could just assign the result of the recursive call to the parent level.

const
 convert = array => array.reduce((o, { subRows = [] }, index) => {
 o[index] = convert(subRows);
 return o;
 }, {}),
 array = [{ index: "1", subRows: [{ index: "2", subRows: undefined }, { index: "3", subRows: undefined }] },{ index: "4", subRows: [{ index: "5", subRows: undefined }] }],
 result = convert(array);
console.log(result);

• C. T.: I don't want to use that index, but actual index.
• C. T.: This looks great. Thanks
• Nina Scholz: please try it. it should work, because it works for the second level without specifying.
• C. T.: I verified, it works for any nesting level. Thanks

Answer 3

Here is an iterative solution using object-scan.

// const objectScan = require('object-scan');
const myArr = [{ index: '1', subRows: [{ index: '2', subRows: undefined }, { index: '3', subRows: undefined }] }, { index: '4', subRows: [{ index: '5', subRows: undefined }] }];
const extract = (arr) => objectScan(['**(^subRows$)'], {
 reverse: false,
 useArraySelector: false,
 breakFn: ({ key, property, context }) => {
 if (!Number.isInteger(property)) {
 return;
 }
 context.length = Math.ceil(key.length / 2);
 const last = context[context.length - 1];
 last[property] = {};
 context.push(last[property]);
 }
})(arr, [{}])[0];
console.log(extract(myArr));
// => { '0': { '0': {}, '1': {} }, '1': { '0': {} } }

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<script src="https://bundle.run/[email protected]"></script>

Disclaimer: I'm the author of object-scan