JS - Transform Nested array of JSON into single Object

Question

I want to transform the nested JSON structure into a single object, with the dynamic key I tried with below code but it's work only with one level, I need to write some recursive function, that I am struggling to write the code for n level of nested JSON. Please advise.

 data.map((e) => {
 for (let key in e) {
 if (typeof e[key] === "object") {
 for (let onLevel in e[key]) {
 e[key + "." + onLevel] = e[key][onLevel];
 }
 }
 }
 });

Example

Input JSON

[{
 "Id": "0hb3L00000000jkQAA",
 "Name": "P-2797",
 "ContactEncounterId": "0ha3L000000001qQAA",
 "StartTime": "2020年06月27日T11:00:00.000Z",
 "EncounterDuration": 25,
 "ContactEncounter": {
 "Name": "Grocery Shopping 17",
 "LocationId": "1313L0000004ENlQAM",
 "Id": "0ha3L000000001qQAA",
 "Location": {
 "Name": "Waitrose",
 "LocationType": "Site",
 "Id": "1313L0000004ENlQAM"
 }
 }
}]

OutPut JSON

[{
 "Id": "0hb3L00000000jkQAA",
 "Name": "P-2797",
 "ContactEncounterId": "0ha3L000000001qQAA",
 "StartTime": "2020年06月27日T11:00:00.000Z",
 "EncounterDuration": 25,
 "ContactEncounter.Name": "Grocery Shopping 17",
 "ContactEncounter.LocationId": "1313L0000004ENlQAM",
 "ContactEncounter.Id": "0ha3L000000001qQAA",
 "ContactEncounter.Location.Name": "Waitrose",
 "ContactEncounter.Location.LocationType": "Site",
 "ContactEncounter.Location.Id": "1313L0000004ENlQAM"
}]

• Andreas: That's not JSON. Input and output are both an array with one object -> What is the difference between JSON and Object Literal Notation?

Answer 1

As you said, you need to create a recursion to get deeper into the object. Which means, you would have to track the path where you are.

You could solve it in the following way

const input = [{
 "Id": "0hb3L00000000jkQAA",
 "Name": "P-2797",
 "ContactEncounterId": "0ha3L000000001qQAA",
 "StartTime": "2020-06-27T11:00:00.000Z",
 "EncounterDuration": 25,
 "ContactEncounter": {
 "Name": "Grocery Shopping 17",
 "LocationId": "1313L0000004ENlQAM",
 "Id": "0ha3L000000001qQAA",
 "Location": {
 "Name": "Waitrose",
 "LocationType": "Site",
 "Id": "1313L0000004ENlQAM"
 }
 }
 }
];
function merge( source, target = {}, ...parents) {
 for (let [key, value] of Object.entries( source ) ) {
 const path = (parents || []).concat( key );
 if (typeof value === 'object') {
 merge( value, target, ...path );
 continue;
 }
 target[path.join('.')] = value;
 }
 return target;
}
console.log( merge( input[0] ) );

Or in the following way, where you just use Object.assign to assign the results of the deeper search into your current object.

const input = [{
 "Id": "0hb3L00000000jkQAA",
 "Name": "P-2797",
 "ContactEncounterId": "0ha3L000000001qQAA",
 "StartTime": "2020-06-27T11:00:00.000Z",
 "EncounterDuration": 25,
 "ContactEncounter": {
 "Name": "Grocery Shopping 17",
 "LocationId": "1313L0000004ENlQAM",
 "Id": "0ha3L000000001qQAA",
 "Location": {
 "Name": "Waitrose",
 "LocationType": "Site",
 "Id": "1313L0000004ENlQAM"
 }
 }
 }
];
function merge( source, ...parents) {
 const mergedValue = {};
 for (let [key, value] of Object.entries( source ) ) {
 const path = (parents || []).concat( key );
 if (typeof value === 'object') {
 Object.assign( mergedValue, merge( value, ...path ) );
 continue;
 }
 mergedValue[path.join('.')] = value;
 }
 return mergedValue;
}
console.log( merge( input[0] ) );

• ak85: This works well thanks unless there is null values eg if LocationType: null. Do you have any thoughts on how to handle this with Object.entries?
• Icepickle: @ak85 well you could check if (value === null || value === undefined) { continue; } and probably ensure that source ain't null or undefined either?
• Edenshaw: You saved me like 2 hours of work on a Friday afternoon!

Answer 2

Here is another approach by using the second parameter and passing the key when finding a nth level object.

const obj = {
 "Id": "0hb3L00000000jkQAA",
 "Name": "P-2797",
 "ContactEncounterId": "0ha3L000000001qQAA",
 "StartTime": "2020-06-27T11:00:00.000Z",
 "EncounterDuration": 25,
 "ContactEncounter": {
 "Name": "Grocery Shopping 17",
 "LocationId": "1313L0000004ENlQAM",
 "Id": "0ha3L000000001qQAA",
 "Location": {
 "Name": "Waitrose",
 "LocationType": "Site",
 "Id": "1313L0000004ENlQAM"
 }
 }
}
function flattenObj(obj, param) {
 let newObj = {};
 for (let key in obj) {
 if (typeof obj[key] === 'object') {
 newObj = { ...newObj,
 ...flattenObj(obj[key], key + '.')
 }
 } else {
 newObj[param + key] = obj[key]
 }
 }
 return newObj;
}
console.log(flattenObj(obj, ''))