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Update existing javascript object with new data recursively. Arrays elements should be merged by id

I've created an update object API that receives new update data of an existing document.
Let's say, I have two objects oldData and newData
oldData = {
me:{
name:{
short:'will'
long:'william'
}
},
friends:[
{
id: 1,
name:{
short:'mike'
long:'michael'
},games:[]
},
{
id: 2,
name:{
short:'fred'
long:'freddy'
}
},
],
favoriteGames:[
'gta',
'animal crossing',
'mortal kombat'
],
favoriteFood:['bacon'],
}
newData = {
me:{
name:{
long:'willy'
longer:'william'
}
},
friends:[
{
id:3,
name:{
short:'max',
long:'maxwell'
}
},
{
id:1,
name:{
short:'mic',
}
},
],
favoriteGames:[
'tekken'
]
}
calling applyUpdate(oldData, newData)should return
result = {
me:{
name:{
short:'will',
long:'willy',
longer:'william'
}
},
friends:[
{
id:3,
name:{
short:'max',
long:'maxwell'
}
},
{
id: 1,
name:{
short:'mic'
long:'michael'
},games:[]
}
],
favoriteGames:[
'tekken'
],
favoriteFood:['bacon'],
}
Basically, the rules for merging are:
If a key in an object is specified with new data, it overrides the
value of the same key in old data.
If a key is not specified, the
value of the same key in old data is kept.
If the value of a key in new data is an array of objects:
Each object must be merged BY id with elements in the array of the same key in old data.
Elements not included in the arrays of newData are removed from the result.
The order of elements in the arrays of newData should be preserved.
Merging must be done deeply, since nested arrays and objects of unspecified depth should be possible.
I've actually successfully implemented this with a horrendously long and ugly recursive function. But am worried about performance and readability issues. I am open to suggestions using lodash or underscore.
Thanks!

Try this. It's hard to write this in a readable way.
function customizer(oldProp, newProp) {
if (Array.isArray(newProp)) {
// check if `newProp` is an array of objects which has property `id`
if (typeof newProp[0] === 'object' && newProp[0].hasOwnProperty('id')) {
if (!Array.isArray(oldProp)) {
return newProp;
}
// merge objects of 2 arrays in `oldProp` and `newProp`
const mergedArr = [];
for (const objNewArr of newProp) {
const objOldArr = oldProp.find(o => o.id === objNewArr.id);
if (objOldArr) {
mergedArr.push(_.merge(objOldArr, objNewArr));
} else {
mergedArr.push(objNewArr);
}
}
return mergedArr;
}
return newProp;
}
if (typeof newProp === 'object') {
return _.merge(oldProp, newProp);
}
return newProp;
}
_.mergeWith(oldData, newData, customizer); // returns the merged object

Here's what worked. Thanks Duc.
function customizer(oldProp, newProp) {
if (Array.isArray(newProp)) {
if (typeof newProp[0] === 'object') {
const mergedArr = [];
for (const objNewArr of newProp) {
const objOldArr = oldProp.find(o => o._id === objNewArr._id);
if (objOldArr) {
mergedArr.push(_.mergeWith(_.cloneDeep(objOldArr), _.cloneDeep(objNewArr), customizer));
} else {
mergedArr.push(objNewArr);
}
}
return mergedArr;
}else{
return newProp;
}
}else if (typeof newProp === 'object') {
return _.merge(oldProp, newProp);
}else{
return undefined;
}
}
var result = _.mergeWith(_.cloneDeep(oldData), _.cloneDeep(newData), customizer); // returns the merged object

React: Calling filter on Object.keys

A React component is passed a state property, which is an object of objects:
{
things: {
1: {
name: 'fridge',
attributes: []
},
2: {
name: 'ashtray',
attributes: []
}
}
}
It is also passed (as a router parameter) a name. I want the component to find the matching object in the things object by comparing name values.
To do this I use the filter method:
Object.keys(this.props.things).filter((id) => {
if (this.props.things[id].name === this.props.match.params.name) console.log('found!');
return (this.props.things[id].name === this.props.match.params.name);
});
However this returns undefined. I know the condition works because of my test line (the console.log line), which logs found to the console. Why does the filter method return undefined?

Object.keys returns an array of keys (like maybe ["2"] in your case).
If you are interested in retrieving the matching object, then you really need Object.values. And if you are expecting one result, and not an array of them, then use find instead of filter:
Object.values(this.props.things).find((obj) => {
if (obj.name === this.props.match.params.name) console.log('found!');
return (obj.name === this.props.match.params.name);
});
Be sure to return that result if you use it within a function. Here is a snippet based on the fiddle you provided in comments:
var state = {
things: {
1: {
name: 'fridge',
attributes: []
},
2: {
name: 'ashtray',
attributes: []
}
}
};
var findThing = function(name) {
return Object.values(state.things).find((obj) => {
if (obj.name === name) console.log('found!');
return obj.name === name;
});
}
var result = findThing('fridge');
console.log(result);

You need to assign the result of filter to a object and you get the result as the [id]. You then need to get the object as this.props.things[id]
var data = {
things: {
1: {
name: 'fridge',
attributes: []
},
2: {
name: 'ashtray',
attributes: []
}
}
}
var name = 'fridge';
var newD = Object.keys(data.things).filter((id) => {
if (data.things[id].name === name) console.log('found!');
return (data.things[id].name === name);
});
console.log(data.things[newD]);

Deleting nested property in javascript object

I have a JS object like this:
var tenants = {
'first': {
'name': 'first',
'expired': 1
},
'second': {
'name': 'second'
}
}
And I'd like to delete the 'expired' property of tenant 'first', should I just do this?
delete tenants['first']['expired'];
Note: this question is more specific than the question: How do I remove a property from a JavaScript object?, in that my question focuses on the 'nested' part.

Yes. That would work.
delete tenants['first']['expired']; or delete tenants.first.expired;.
If you are deleting it only because you wanted to exclude it from JSON.stringify(), you can also just set it to undefined, like tenants['first']['expired'] = undefined;

If the property you want to delete is stored in a string, you can use this function
function deletePropertyPath (obj, path) {
if (!obj || !path) {
return;
}
if (typeof path === 'string') {
path = path.split('.');
}
for (var i = 0; i < path.length - 1; i++) {
obj = obj[path[i]];
if (typeof obj === 'undefined') {
return;
}
}
delete obj[path.pop()];
};
Example Usage
var tenants = {
'first': {
'name': 'first',
'expired': 1
},
'second': {
'name': 'second'
}
}
var property = 'first.expired';
deletePropertyPath(tenants, property);

If your app is using lodash, then _.unset is a safe way for deleting nested properties. You can specify nested keys without worrying about their existence.
let games = { 'hitman': [{ 'agent': { 'id': 47 } }] };
_.unset(games, 'hitman[0].agent.id');
_.unset(games, 'hitman[0].muffin.cupcake'); // won't break
further reading: https://lodash.com/docs/4.17.15#unset

I came up with this:
const deleteByPath = (object, path) => {
let currentObject = object
const parts = path.split(".")
const last = parts.pop()
for (const part of parts) {
currentObject = currentObject[part]
if (!currentObject) {
return
}
}
delete currentObject[last]
}
Usage:
deleteByPath({ "a" : { "b" : true }},"a.b")

If you want to delete a property with a particular name in an arbitrarily deep object, I would recommend that you use a battle-tested library. You can use DeepDash, an extension to Lodash.
// Recursively remove any "expired" properties
_.eachDeep(e, (child, prop, parent, ctx):boolean => {
if (prop === 'expired') {
delete parent[prop];
return false; // per docs, this means do not recurse into this child
}
return true;
});
And if you would rather have a new copy (rather than mutating the existing object), DeepDash also has an omitDeep function you can use that will return the new object.

If you have the path of the key separated by ., say first.expired in your case, you can do deleteKey(tenants, 'first.expired'):
const deleteKey = (obj, path) => {
const _obj = JSON.parse(JSON.stringify(obj));
const keys = path.split('.');
keys.reduce((acc, key, index) => {
if (index === keys.length - 1) {
delete acc[key];
return true;
}
return acc[key];
}, _obj);
return _obj;
}
let tenants = {
'first': {
'name': 'first',
'expired': 1
},
'second': {
'name': 'second'
}
};
const PATH_TO_DELETE = 'first.expired';
tenants = deleteKey(tenants, PATH_TO_DELETE);
console.log('DELETE SUCCESSFUL:', tenants);

With modern JS you can simple do it this way:
const tenants = {
first: {
name: 'first',
expired: 1
},
second: {
name: 'second'
}
}
delete tenants?.first?.expired;
delete tenants?.second?.expired;
delete tenants?.third?.expired;
console.log(tenants);
By using optional chaining you're able to safely try to remove nested properties on objects that might not exist.
Check the mdn site to check browser compatibility
NOTE: Optional chaining does also works with braces

Redux ES6 (BabelJS): is there a map function that can iterate this structure?

{
'1': {
id: 1,
parent_id: 0,
elementType: 'view',
style: {color: 'green'},
selected: false,
childIds: [2]
},
'2': {
id: 2,
parent_id: 1,
elementType: 'text',
style: {color: 'green'},
selected: true,
childIds: []
}
}
It's for a reducer and I'd love to be able to do this:
obj.map(([key, value])=> {
if (value.id === 1) {
return {...value, selected:false};
} else {
return value;
}
});
I thought maybe using this but it will probably won't play well with redux mapping.
UPDATE:
Following the recommendation here I've tried building a new map function. This version is what I came with:
const map = (object, callback) => {
return Object.keys(object).reduce(function(output, key) {
output[key] = callback.call(this, object[key]);
return output;
}, {});
}
And I a trying to use it like this (an example):
let newState = map(oldState, element => {
if (element.id === 1) {
return {...element, selected:false};
} else {
return {...element};
}
});
Meanwhile the tests are passing.

Try using Object.keys(), it will let you traverse through object keys, that way you will be able to access specific value.

You can try using Object.entries. It's still a proposal, but I think it's already hidden behind some babel stage flag.
for (const [key, value] of Object.entries(obj)) {
//do whatever you want
}
ES proposal: Object.entries() and Object.values()

find and modify deeply nested object in javascript array

I have an array of objects that can be of any length and any depth. I need to be able to find an object by its id and then modify that object within the array. Is there an efficient way to do this with either lodash or pure js?
I thought I could create an array of indexes that led to the object but constructing the expression to access the object with these indexes seems overly complex / unnecessary
edit1; thanks for all yours replies I will try and be more specific. i am currently finding the location of the object I am trying to modify like so. parents is an array of ids for each parent the target object has. ancestors might be a better name for this array. costCenters is the array of objects that contains the object I want to modify. this function recurses and returns an array of indexes that lead to the object I want to modify
var findAncestorsIdxs = function(parents, costCenters, startingIdx, parentsIdxs) {
var idx = startingIdx ? startingIdx : 0;
var pidx = parentsIdxs ? parentsIdxs : [];
_.each(costCenters, function(cc, ccIdx) {
if(cc.id === parents[idx]) {
console.log(pidx);
idx = idx + 1;
pidx.push(ccIdx);
console.log(pidx);
pidx = findAncestorsIdx(parents, costCenters[ccIdx].children, idx, pidx);
}
});
return pidx;
};
Now with this array of indexes how do I target and modify the exact object I want? I have tried this where ancestors is the array of indexes, costCenters is the array with the object to be modified and parent is the new value to be assigned to the target object
var setParentThroughAncestors = function(ancestors, costCenters, parent) {
var ccs = costCenters;
var depth = ancestors.length;
var ancestor = costCenters[ancestors[0]];
for(i = 1; i < depth; i++) {
ancestor = ancestor.children[ancestors[i]];
}
ancestor = parent;
console.log(ccs);
return ccs;
};
this is obviously just returning the unmodified costCenters array so the only other way I can see to target that object is to construct the expression like myObjects[idx1].children[2].grandchildren[3].ggranchildren[4].something = newValue. is that the only way? if so what is the best way to do that?

You can use JSON.stringify for this. It provides a callback for each visited key/value pair (at any depth), with the ability to skip or replace.
The function below returns a function which searches for objects with the specified ID and invokes the specified transform callback on them:
function scan(id, transform) {
return function(obj) {
return JSON.parse(JSON.stringify(obj, function(key, value) {
if (typeof value === 'object' && value !== null && value.id === id) {
return transform(value);
} else {
return value;
}
}));
}
If as the problem is stated, you have an array of objects, and a parallel array of ids in each object whose containing objects are to be modified, and an array of transformation functions, then it's just a matter of wrapping the above as
for (i = 0; i < objects.length; i++) {
scan(ids[i], transforms[i])(objects[i]);
}
Due to restrictions on JSON.stringify, this approach will fail if there are circular references in the object, and omit functions, regexps, and symbol-keyed properties if you care.
See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_native_JSON#The_replacer_parameter for more info.

As Felix Kling said, you can iterate recursively over all objects.
// Overly-complex array
var myArray = {
keyOne: {},
keyTwo: {
myId: {a: '3'}
}
};
var searchId = 'myId', // Your search key
foundValue, // Populated with the searched object
found = false; // Internal flag for iterate()
// Recursive function searching through array
function iterate(haystack) {
if (typeof haystack !== 'object' || haystack === null) return; // type-safety
if (typeof haystack[searchId] !== 'undefined') {
found = true;
foundValue = haystack[searchId];
return;
} else {
for (var i in haystack) {
// avoid circular reference infinite loop & skip inherited properties
if (haystack===haystack[i] || !haystack.hasOwnProperty(i)) continue;
iterate(haystack[i]);
if (found === true) return;
}
}
}
// USAGE / RESULT
iterate(myArray);
console.log(foundValue); // {a: '3'}
foundValue.b = 4; // Updating foundValue also updates myArray
console.log(myArray.keyTwo.myId); // {a: '3', b: 4}
All JS object assignations are passed as reference in JS. See this for a complete tutorial on objects :)
Edit: Thanks #torazaburo for suggestions for a better code.

If each object has property with the same name that stores other nested objects, you can use: https://github.com/dominik791/obj-traverse
findAndModifyFirst() method should solve your problem. The first parameter is a root object, not array, so you should create it at first:
var rootObj = {
name: 'rootObject',
children: [
{
'name': 'child1',
children: [ ... ]
},
{
'name': 'child2',
children: [ ... ]
}
]
};
Then use findAndModifyFirst() method:
findAndModifyFirst(rootObj, 'children', { id: 1 }, replacementObject)
replacementObject is whatever object that should replace the object that has id equal to 1.
You can try it using demo app:
https://dominik791.github.io/obj-traverse-demo/

Here's an example that extensively uses lodash. It enables you to transform a deeply nested value based on its key or its value.
const _ = require("lodash")
const flattenKeys = (obj, path = []) => (!_.isObject(obj) ? { [path.join('.')]: obj } : _.reduce(obj, (cum, next, key) => _.merge(cum, flattenKeys(next, [...path, key])), {}));
const registrations = [{
key: "123",
responses:
{
category: 'first',
},
}]
function jsonTransform (json, conditionFn, modifyFn) {
// transform { responses: { category: 'first' } } to { 'responses.category': 'first' }
const flattenedKeys = Object.keys(flattenKeys(json));
// Easily iterate over the flat json
for(let i = 0; i < flattenedKeys.length; i++) {
const key = flattenedKeys[i];
const value = _.get(json, key)
// Did the condition match the one we passed?
if(conditionFn(key, value)) {
// Replace the value to the new one
_.set(json, key, modifyFn(key, value))
}
}
return json
}
// Let's transform all 'first' values to 'FIRST'
const modifiedCategory = jsonTransform(registrations, (key, value) => value === "first", (key, value) => value = value.toUpperCase())
console.log('modifiedCategory --', modifiedCategory)
// Outputs: modifiedCategory -- [ { key: '123', responses: { category: 'FIRST' } } ]

I needed to modify deeply nested objects too, and found no acceptable tool for that purpose. Then I've made this and pushed it to npm.
https://www.npmjs.com/package/find-and
This small [TypeScript-friendly] lib can help with modifying nested objects in a lodash manner. E.g.,
var findAnd = require("find-and");
const data = {
name: 'One',
description: 'Description',
children: [
{
id: 1,
name: 'Two',
},
{
id: 2,
name: 'Three',
},
],
};
findAnd.changeProps(data, { id: 2 }, { name: 'Foo' });
outputs
{
name: 'One',
description: 'Description',
children: [
{
id: 1,
name: 'Two',
},
{
id: 2,
name: 'Foo',
},
],
}
https://runkit.com/embed/bn2hpyfex60e
Hope this could help someone else.

I wrote this code recently to do exactly this, as my backend is rails and wants keys like:
first_name
and my front end is react, so keys are like:
firstName
And these keys are almost always deeply nested:
user: {
firstName: "Bob",
lastName: "Smith",
email: "bob#email.com"
}
Becomes:
user: {
first_name: "Bob",
last_name: "Smith",
email: "bob#email.com"
}
Here is the code
function snakeCase(camelCase) {
return camelCase.replace(/([A-Z])/g, "_$1").toLowerCase()
}
export function snakeCasedObj(obj) {
return Object.keys(obj).reduce(
(acc, key) => ({
...acc,
[snakeCase(key)]: typeof obj[key] === "object" ? snakeCasedObj(obj[key]) : obj[key],
}), {},
);
}
Feel free to change the transform to whatever makes sense for you!