Develop Reference

Being able to remove duplicate keys from an array of objects

I have a question about how I can delete the existing elements, for example, in my case "Tallas" is repeated, could you please help me? Thank you very much to those who are willing to help me to solve this problem
const data =
[ { atributos: { Tallas: [{ id: 0, name: 'XS' }, { id: 1, name: 'S' }] }}
, { atributos: { Calzado: [{ id: 0, name: '10' }, { id: 1, name: '9.5' }] }}
, { atributos: { Tallas: [{ id: 0, name: 'XS' }] }}
]
The idea is to have this json format with the last "Tallas" since it is the last one that I added through my dynamic form.
const expected =
[{ atributos: { Calzado: [{ id: 0, name: '10' }, { id: 1, name: '9.5' }] }}
, { atributos: { Tallas: [{ id: 0, name: 'XS' }] }}
]
How do I do this is there a way to do it, I've tried with filter plus the findindex but I can't get to eliminate the repetition of the json res= new.filter((arr, index, self) => index === self.findIndex( (t) => (t.attributes === arr.attributes )))

To unique the array of objects, we can use the Javascript Set module, if the array has complex nested objects, we can stringify each object before creating new Set data. this below function will unique the array of complex objects.
function unique_array(array = []) {
const newSetData = new Set(array.map((e) => JSON.stringify(e)));
return Array.from(newSetData).map((e) => JSON.parse(e));
}

this is a function that takes an array and return the same array but delete every duplicated item
function removeDuplicates(arr) {
return arr.filter((item,
index) => arr.indexOf(item) === index);
}
I didn't understant the part written in spanish so I hope this is what you are looking for

This is a solution specific to your question. this is not a generic solution.
const data = [
{
atributos: {
Tallas: [
{ id: 0, name: "XS" },
{ id: 1, name: "S" },
],
},
},
{
atributos: {
Calzado: [
{ id: 0, name: "10" },
{ id: 1, name: "9.5" },
],
},
},
{
atributos: {
Tallas: [
{ id: 0, name: "XS" },
{ id: 1, name: "S" },
],
},
},
];
function uniqueArray(array) {
const resultObject = array.reduce((acc, eachValue) => {
let keys = Object.keys(eachValue.atributos);
keys.forEach((eachKey) => {
if (!acc[eachKey]) {
acc[eachKey] = [];
}
let list = eachValue["atributos"][eachKey].map(
(each) => each.id + "-" + each.name
);
acc[eachKey].push(...list);
});
return acc;
}, {});
const resultArray = Object.keys(resultObject).reduce((acc, each) => {
let setData = Array.from(new Set(resultObject[each]));
acc.push({
atributos: {
[each]: setData.map((e) => {
return { id: e.split("-")[0], name: e.split("-")[1] };
}),
},
});
return acc;
}, []);
return resultArray;
}
const result = uniqueArray(data)
console.log("result ", JSON.stringify(result, null, 2));

How to loop the object inside key's object in react js [duplicate]

How would I find all values by specific key in a deep nested object?
For example, if I have an object like this:
const myObj = {
id: 1,
children: [
{
id: 2,
children: [
{
id: 3
}
]
},
{
id: 4,
children: [
{
id: 5,
children: [
{
id: 6,
children: [
{
id: 7,
}
]
}
]
}
]
},
]
}
How would I get an array of all values throughout all nests of this obj by the key of id.
Note: children is a consistent name, and id's won't exist outside of a children object.
So from the obj, I would like to produce an array like this:
const idArray = [1, 2, 3, 4, 5, 6, 7]

This is a bit late but for anyone else finding this, here is a clean, generic recursive function:
function findAllByKey(obj, keyToFind) {
return Object.entries(obj)
.reduce((acc, [key, value]) => (key === keyToFind)
? acc.concat(value)
: (typeof value === 'object')
? acc.concat(findAllByKey(value, keyToFind))
: acc
, [])
}
// USAGE
findAllByKey(myObj, 'id')

You could make a recursive function like this:
idArray = []
function func(obj) {
idArray.push(obj.id)
if (!obj.children) {
return
}
obj.children.forEach(child => func(child))
}
Snippet for your sample:
const myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
}
idArray = []
function func(obj) {
idArray.push(obj.id)
if (!obj.children) {
return
}
obj.children.forEach(child => func(child))
}
func(myObj)
console.log(idArray)

I found steve's answer to be most suited for my needs in extrapolating this out and creating a general recursive function. That said, I encountered issues when dealing with nulls and undefined values, so I extended the condition to accommodate for this. This approach uses:
Array.reduce() - It uses an accumulator function which appends the value's onto the result array. It also splits each object into it's key:value pair which allows you to take the following steps:
Have you've found the key? If so, add it to the array;
If not, have I found an object with values? If so, the key is possibly within there. Keep digging by calling the function on this object and append the result onto the result array; and
Finally, if this is not an object, return the result array unchanged.
Hope it helps!
const myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
}
function findAllByKey(obj, keyToFind) {
return Object.entries(obj)
.reduce((acc, [key, value]) => (key === keyToFind)
? acc.concat(value)
: (typeof value === 'object' && value)
? acc.concat(findAllByKey(value, keyToFind))
: acc
, []) || [];
}
const ids = findAllByKey(myObj, 'id');
console.log(ids)

You can make a generic recursive function that works with any property and any object.
This uses Object.entries(), Object.keys(), Array.reduce(), Array.isArray(), Array.map() and Array.flat().
The stopping condition is when the object passed in is empty:
const myObj = {
id: 1,
anyProp: [{
id: 2,
thing: { a: 1, id: 10 },
children: [{ id: 3 }]
}, {
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{ id: 7 }]
}]
}]
}]
};
const getValues = prop => obj => {
if (!Object.keys(obj).length) { return []; }
return Object.entries(obj).reduce((acc, [key, val]) => {
if (key === prop) {
acc.push(val);
} else {
acc.push(Array.isArray(val) ? val.map(getIds).flat() : getIds(val));
}
return acc.flat();
}, []);
}
const getIds = getValues('id');
console.log(getIds(myObj));

Note: children is a consistent name, and id's wont exist outside
of a children object.
So from the obj, I would like to produce an array like this:
const idArray = [1, 2, 3, 4, 5, 6, 7]
Given that the question does not contain any restrictions on how the output is derived from the input and that the input is consistent, where the value of property "id" is a digit and id property is defined only within "children" property, save for case of the first "id" in the object, the input JavaScript plain object can be converted to a JSON string using JSON.stringify(), RegExp /"id":\d+/g matches the "id" property and one or more digit characters following the property name, which is then mapped to .match() the digit portion of the previous match using Regexp \d+ and convert the array value to a JavaScript number using addition operator +
const myObject = {"id":1,"children":[{"id":2,"children":[{"id":3}]},{"id":4,"children":[{"id":5,"children":[{"id":6,"children":[{"id":7}]}]}]}]};
let res = JSON.stringify(myObject).match(/"id":\d+/g).map(m => +m.match(/\d+/));
console.log(res);
JSON.stringify() replacer function can alternatively be used to .push() the value of every "id" property name within the object to an array
const myObject = {"id":1,"children":[{"id":2,"children":[{"id":3}]},{"id":4,"children":[{"id":5,"children":[{"id":6,"children":[{"id":7}]}]}]}]};
const getPropValues = (o, prop) =>
(res => (JSON.stringify(o, (key, value) =>
(key === prop && res.push(value), value)), res))([]);
let res = getPropValues(myObject, "id");
console.log(res);
Since the property values of the input to be matched are digits, all the JavaScript object can be converted to a string and RegExp \D can be used to replace all characters that are not digits, spread resulting string to array, and .map() digits to JavaScript numbers
let res = [...JSON.stringify(myObj).replace(/\D/g,"")].map(Number)

Using recursion.
const myObj = { id: 1, children: [ { id: 2, children: [ { id: 3 } ] }, { id: 4, children: [ { id: 5, children: [ { id: 6, children: [ { id: 7, } ] } ] } ] }, ]},
loop = (array, key, obj) => {
if (!obj.children) return;
obj.children.forEach(c => {
if (c[key]) array.push(c[key]); // is not present, skip!
loop(array, key, c);
});
},
arr = myObj["id"] ? [myObj["id"]] : [];
loop(arr, "id", myObj);
console.log(arr);
.as-console-wrapper { max-height: 100% !important; top: 0; }

You can make a recursive function with Object.entries like so:
const myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
};
function findIds(obj) {
const entries = Object.entries(obj);
let result = entries.map(e => {
if (e[0] == "children") {
return e[1].map(child => findIds(child));
} else {
return e[1];
}
});
function flatten(arr, flat = []) {
for (let i = 0, length = arr.length; i < length; i++) {
const value = arr[i];
if (Array.isArray(value)) {
flatten(value, flat);
} else {
flat.push(value);
}
}
return flat;
}
return flatten(result);
}
var ids = findIds(myObj);
console.log(ids);
Flattening function from this answer
ES5 syntax:
var myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
};
function findIds(obj) {
const entries = Object.entries(obj);
let result = entries.map(function(e) {
if (e[0] == "children") {
return e[1].map(function(child) {
return findIds(child)
});
} else {
return e[1];
}
});
function flatten(arr, flat = []) {
for (let i = 0, length = arr.length; i < length; i++) {
const value = arr[i];
if (Array.isArray(value)) {
flatten(value, flat);
} else {
flat.push(value);
}
}
return flat;
}
return flatten(result);
}
var ids = findIds(myObj);
console.log(ids);

let str = JSON.stringify(myObj);
let array = str.match(/\d+/g).map(v => v * 1);
console.log(array); // [1, 2, 3, 4, 5, 6, 7]

We use object-scan for a lot of our data processing needs now. It makes the code much more maintainable, but does take a moment to wrap your head around. Here is how you could use it to answer your question
// const objectScan = require('object-scan');
const find = (data, needle) => objectScan([needle], { rtn: 'value' })(data);
const myObj = { id: 1, children: [{ id: 2, children: [ { id: 3 } ] }, { id: 4, children: [ { id: 5, children: [ { id: 6, children: [ { id: 7 } ] } ] } ] }] };
console.log(find(myObj, '**.id'));
// => [ 7, 6, 5, 4, 3, 2, 1 ]
.as-console-wrapper {max-height: 100% !important; top: 0}
<script src="https://bundle.run/object-scan#13.7.1"></script>
Disclaimer: I'm the author of object-scan

import {flattenDeep} from 'lodash';
/**
* Extracts all values from an object (also nested objects)
* into a single array
*
* #param obj
* #returns
*
* #example
* const test = {
* alpha: 'foo',
* beta: {
* gamma: 'bar',
* lambda: 'baz'
* }
* }
*
* objectFlatten(test) // ['foo', 'bar', 'baz']
*/
export function objectFlatten(obj: {}) {
const result = [];
for (const prop in obj) {
const value = obj[prop];
if (typeof value === 'object') {
result.push(objectFlatten(value));
} else {
result.push(value);
}
}
return flattenDeep(result);
}

Below solution is generic which will return all values by matching nested keys as well e.g for below json object
{
"a":1,
"b":{
"a":{
"a":"red"
}
},
"c":{
"d":2
}
}
to find all values matching key "a" output should be return
[1,{a:"red"},"red"]
const findkey = (obj, key) => {
let arr = [];
if (isPrimitive(obj)) return obj;
for (let [k, val] of Object.entries(obj)) {
if (k === key) arr.push(val);
if (!isPrimitive(val)) arr = [...arr, ...findkey(val, key)];
}
return arr;
};
const isPrimitive = (val) => {
return val !== Object(val);
};

Find the unique id of the item and group its value in array using reduce method?

Please help me to find the expected output from the given scenario
input array:
const items = [
{ id: 1, name: "a" },
{ id: 2, name: "b" },
{ id: 3, name: "c" },
{ id: 1, name: "d" },
{ id: 3, name: "f" },
{ id: 1, name: "a" },
{ id: 3, name: "c" },
]
expected output:
[{ id: 1, names: ['a', 'd']},
{ id: 2, names: ['b']},
{ id: 3, names: ['c', 'f']}]

You can create a new array, loop through your main array and check if there is an object with the current id in the new array and update it or create a new object accordingly.
Like this:
let newItems = [];
items.forEach(item => {
let index = newItems.findIndex(el => el.id == item.id);
if (index > -1) {
if (newItems[index]['names'].indexOf(item.name) === -1) {
return newItems[index]['names'].push(item.name)
}
} else {
newItems.push({id: item.id, names: [item.name]});
}
});
With reduce method:
const newArr = items.reduce((pv, cv) => {
let index = pv.findIndex(el => el.id == cv.id);
if (index > -1) {
if (pv[index]['names'].indexOf(cv.name) === -1) {
pv[index]['names'].push(cv.name)
}
} else {
pv.push({id: cv.id, names: [cv.name]});
}
return pv;
}, []);
pv is previous value which is the new array, cv is current value which is each object in items array. Initial value of newArr is []

You can use spread operator and retrieve the values of the duplicate key and push it in the new array of objects.
Thanks & Regards

How can add properties to my objects based on the duplicates inside the array?

I have this array of objects
let arr = [
{
id: 1,
},
{
id: 1,
},
{
id: 2,
},
{
id: 1,
},
{
id:4,
},
{
id: 3,
},
{
id:4,
}
]
i need to find and change every object in the array based on condition.
So if there are duplicates in the array i need to set on my objects 100 except last duplicate where i should have 200.
If i don't have any duplicates than i should have again 200
So the output shpuld be
let arr = [
{
id: 1,
number: 100
},
{
id: 1,
number: 100
},
{
id: 2,
number: 200
},
{
id: 1,
number: 200
},
{
id:4,
number: 100
},
{
id: 3,
number: 200
},
{
id:4,
number: 200
}
]
so id 1 has duplicates.
That is why the fiurst occurences are set with number:100 and the last one i set with number:200.
Id 2 has number 200 because there are no duplicates and it is first occurance in the list.
what i tried
I got stuck at
for(let item of arr) {
for(let item2 of arr) {
if(item.id === item2.id) {
item.number = 100;
} else {
item.number = 200;
}
}
}

You can simply iterate through the array in reverse and track which ids you've seen, here using a Set.
const arr = [{ id: 1, }, { id: 1, }, { id: 2, }, { id: 1, }, { id: 4, }, { id: 3, }, { id: 4, }]
let i = arr.length;
const seen = new Set();
while (i--) {
arr[i].number = seen.has(arr[i].id) ? 100 : 200;
seen.add(arr[i].id)
}
console.log(arr)

You can use array.map() to iterate over your array. I think it can provide a nice and concise solution:
const result = arr.map((item, index) => {
const duplicate = arr.filter((_, indx) => indx > index).some((i) => i.id === item.id);
return { ...item, number: duplicate ? 100 : 200 }
});
console.log(result);

We can simply achieve it via Array.map() along with Array.indexOf() & Array.lastIndexOf() methods.
Working Demo :
// Input array
let arr = [{
id: 1,
}, {
id: 1,
}, {
id: 2,
}, {
id: 1,
}, {
id:4,
}, {
id: 3,
}, {
id:4,
}];
// Getting ID's from each object and create a seperate array
let idArr = arr.map(function(item) { return item.id });
// Iterating through the id's array and assigning number property to an original array as per the requirement.
idArr.forEach((item, index) => {
if (idArr.indexOf(item) === idArr.lastIndexOf(item)) {
arr[index].number = 200;
} else {
arr[index].number = 100;
arr[idArr.lastIndexOf(item)].number = 200;
}
});
// Result
console.log(arr);

nested for loops to get another object-array output

I need to multiply all the "values" inside "obj1" with the "percent' inside obj2 based on the id of each object. What would be the best way to do that? I've tried with for loop and reduce but I wasn't successful. Any help will be appreciated.
const obj1 = [ { id: 1, value: 10 }, { id: 2, value: 10 } ]
const obj2 = {
len: {
id: 1,
nj: "321345",
percent: 0.05,
},
wor: {
id: 2,
nj: "321345",
percent: 0.1,
}
}
outputExpected: [ { id: 1, value: 0.5 }, { id: 2, value: 1 } ]

You can do that by going through and matching the ids. there are some optimizations that can be made if they are sorted however.
const obj1 = [ { id: 1, value: 10 }, { id: 2, value: 10 } ]
const obj2 = {
len: {
id: 1,
nj: "321345",
percent: 0.05,
},
wor: {
id: 2,
nj: "321345",
percent: 0.1,
}
}
const x = Object.keys(obj2).map((key,index)=>{
const { id, value } = obj1.find(({id})=>id===obj2[key].id)
return ({id,value:value*obj2[key].percent})
})
console.log(x)
//outputExpected: [ { id: 1, value: 0.5 }, { id: 2, value: 1 } ]

You can first create a lookup map using Map, then loop over the obj1 using map to get the desired result
const obj1 = [
{ id: 1, value: 10 },
{ id: 2, value: 10 },
];
const obj2 = {
len: {
id: 1,
nj: "321345",
percent: 0.05,
},
wor: {
id: 2,
nj: "321345",
percent: 0.1,
},
};
const map = new Map();
Object.values(obj2).forEach((v) => map.set(v.id, v));
const result = obj1.map((o) => ({ ...o, value: o.value * map.get(o.id).percent }));
console.log(result);

This should work for you but doesnt handle exeptions if the id doesnt exist in both objects.
// First get the values in an array for easier manipulation
const aux = Object.values(obj2)
const output = obj1.map(ob => {
// Find the id in the other array.
const obj2Ob = aux.find(o => o.id === ob.id) // The id must exist in this aproach
return {
id: ob.id,
value: ob.value * obj2Ob.percent
}
})
console.log(output) // [ { id: 1, value: 0.5 }, { id: 2, value: 1 } ]