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How to deep filter in array with objects in JS

I have an array and want to get just object { id: 4, name: 'name4' },
const example = [
{
id: '1234',
desc: 'sample1',
items: [
{ id: 1, name: 'name1' },
{ id: 2, name: 'testItem2' }
]
},
{
id: '3456',
desc: 'sample2',
items: [
{ id: 4, name: 'name4' },
{ id: 5, name: 'testItem5' }
]
},
I try in this way.
const name = 'name4';
example.forEach((item) => item.items.find((i) => i.name === name));
But get undefined.

You can using flatMap() to do it
const example = [
{
id: '1234',
desc: 'sample1',
items: [
{ id: 1, name: 'name1' },
{ id: 2, name: 'testItem2' }
]
},
{
id: '3456',
desc: 'sample2',
items: [
{ id: 4, name: 'name4' },
{ id: 5, name: 'testItem5' }
]
}]
const name = 'name4';
let result = example.flatMap(e => e.items).filter(d => d.name == name)
console.log(result)

this way...?
const example =
[ { id : '1234'
, desc : 'sample1'
, items:
[ { id: 1, name: 'name1' }
, { id: 2, name: 'testItem2' }
] }
, { id : '3456'
, desc : 'sample2'
, items:
[ { id: 4, name: 'name4' }
, { id: 5, name: 'testItem5' }
] } ];
const rechName = (s,arr) =>
arr.find( x => // find the first parent object
x.items.some( y => // containing the search
y.name === s )
)?.items // if one
.find( z => z.name === s ); // find it in!
console.log( rechName('name4', example) ) // -> { id: 4, name: 'name4' }
console.log( rechName('abc', example) ) // -> undefined

forEach doesn't do what you think it does. From the docs:
The forEach() method executes a provided function once for each array element.
...
Return value
undefined.
So if you want to use forEach you need to save the value:
const example =
[ { id : '1234'
, desc : 'sample1'
, items:
[ { id: 1, name: 'name1' }
, { id: 2, name: 'testItem2' }
] }
, { id : '3456'
, desc : 'sample2'
, items:
[ { id: 4, name: 'name4' }
, { id: 5, name: 'testItem5' }
] } ]
const results = []; // Store matches here
const name = 'name4';
example.forEach((item) => {
const res = item.items.find((i) => i.name === name);
if (res !== undefined) {
results.push(res);
}
});
console.log(results);
IMHO I would suggest a more functional approach using flatMap and filter instead of forEach.
Lastly, note that in my above snippet, I'm storing the results in an array as it's not entirely clear to me that you won't have multiple matches per your example. But if you're sure that you will only ever have one result then a simple for loop works better, especially if you have a large array of items:
let result = null;
for (let i = 0; i < example.length; i++) {
const res = example[i].items.find((j) => j.name === name);
if (res !== undefined) {
result = res;
break; // No need to iterate further
}
}
console.log(result);

You could use a recursive search function. Here's a detailed example:
// Applies the function recursively from the top of the data tree ("depth-first")
const
data = getData(),
id = 4,
result = findById(data, id);
console.log(result ?? `No item with id ${id} found`);
// Defines the function
function findById(haystack, needleId){
let needle = null; // Defaults to null if no match at or below this level
// Iterates through all the items at this level
for(const item of haystack){
if(item.id == needleId){
// Qapla': Quits early, passes honorable item up to previous level
needle = item;
return needle;
}
else {
// Checks children, grandchildren, etc, before continuing iteration
const nextHaystack = item.items;
if(nextHaystack?.length){
needle = findById(nextHaystack, needleId); // Recursive call
}
}
// Done searching children, continues to next iteration at this level
}
// Done searching this level, returns result up to previous level
return needle;
}
// Gets the initial data
function getData(){
return [
{
id: '1234',
desc: 'sample1',
items: [ { id: 1, name: 'name1' }, { id: 2, name: 'testItem2' } ]
},
{
id: '3456',
desc: 'sample2',
items: [ { id: 4, name: 'name4' }, { id: 5, name: 'testItem5' } ]
}
];
}

How to change value in array with objects in JS

I have an array and want to change name in object { id: 4, name: 'name4' } to 'name6'
const example = [
{
id: '1234',
desc: 'sample1',
items: [
{ id: 1, name: 'name1' },
{ id: 2, name: 'testItem2' }
]
},
{
id: '3456',
desc: 'sample2',
items: [
{ id: 4, name: 'name4' },
{ id: 5, name: 'testItem5' }
]
},
I try in this way but it isn't working
const name = 'name4';
const result = example?.forEach((group) =>
group.items.forEach((item) =>
if (item.name === name) {
return item.name === 'name6';
}
return null;
})
);

The for...of statement is my recommendation for readability and loop optimisation.
const example = [
{
id: '1234',
desc: 'sample1',
items: [
{ id: 1, name: 'name1' },
{ id: 2, name: 'testItem2' },
],
},
{
id: '3456',
desc: 'sample2',
items: [
{ id: 4, name: 'name4' },
{ id: 5, name: 'testItem5' },
],
},
];
const oldName = 'name4';
const newName = 'name6';
for (const group of example) {
for (const item of group.items) {
if (item.name === oldName) {
item.name === newName;
break
}
}
}
You could even go a step further and terminate the outer loop with a label if you only need to change the name in a single group.
outerLoop: for (const group of example) {
for (const item of group.items) {
if (item.name === oldName) {
item.name === newName;
break outerLoop;
}
}
}
Hope this helps.

You could either change the value by simply assigning a new value.
example[1].items[0].name = 'name6'
But you can also iterate through all items and search for the name you want to change. I created a function that goes through an array and loops over its nested items arrays searching for any given name (targetName) and replacing it with a new one (newName):
function changeName(array, targetName, newName) {
// Loop through the elements of array
array.forEach((element) => {
// Check each item: change the name if it matches the target
element.items.forEach((item) => {
if (item.name === targetName) item.name = newName;
});
});
}
// This function will check example array and change
// every name that has a value 'name4' into 'name6'
changeName(example, "name4", "name6");

forEach doesn't return any value.
Instead of return item.name === 'name6' you can simply set new value to item.name.

Why not like this?
const example = [{
id: '1234',
desc: 'sample1',
items: [{
id: 1,
name: 'name1'
},
{
id: 2,
name: 'testItem2'
}
]
},
{
id: '3456',
desc: 'sample2',
items: [{
id: 4,
name: 'name4'
},
{
id: 5,
name: 'testItem5'
}
]
},
]
example[1].items[0].name = 'name6'
console.log(example)

How to recursively transform an array of nested objects into array of flat objects?

I have the following array of deeply nested objects:
const data = [
{
name: "foo",
children:[
{
count: 1,
name: "A"
},
{
count: 2,
name: "B"
}
]
},
{
name: "bar",
children: [
{
count: 3,
name: "C",
children: [
{
count: 4,
name: "D"
}
]
}
]
}
]
The way I'd like to transform this would be such as:
const expectedStructure = [
{
count: 1,
name: "A",
label: "foo = A"
},
{
count: 2,
name: "B",
label: "foo = B"
},
{
count: 3,
name: "C",
label: "bar = C"
},
{
count: 4,
name: "D",
label: "bar = D"
}
]
I created recursive function that transforms nested array into array of flat objects.
Here's my code:
function getChildren(array, result=[]) {
array.forEach(({children, ...rest}) => {
result.push(rest);
if(children) {
getChildren(children, result);
}
});
return result;
}
And here's output I get:
[ { name: 'foo' },
{ count: 1, name: 'A' },
{ count: 2, name: 'B' },
{ name: 'bar' },
{ count: 3, name: 'C' },
{ count: 4, name: 'D' } ]
The problem is that I need to add label field to every object in my output array, and I can't find a solution without iterating multiple times through the final array to make desired transformation. How to properly insert label field without hugely augmenting complexity of the function?

Check each iteration whether the current item is a "parent" item, and reassign label if it is.
const data = [{name:"foo",children:[{count:1,name:"A"},{count:2,name:"B"}]},{name:"bar",children:[{count:3,name:"C",children:[{count:4,name:"D"}]}]}];
function getChildren(array, result = [], label = "") {
array.forEach(({ children, name, count }) => {
if (!label || name[1]) {
label = `${name} = `;
}
if (count) {
result.push({ count, name, label: label + name });
}
if (children) {
getChildren(children, result, label);
}
});
return result;
}
const res = getChildren(data);
console.log(res);

You can use a different function for the nested levels, so you can pass the top-level name properties down through all those recursion levels.
function getTopChildren(array, result = []) {
array.forEach(({
name,
children
}) => {
if (children) {
getChildren(children, name, result);
}
});
return result;
}
function getChildren(array, name, result) {
array.forEach(({
children,
...rest
}) => {
rest.label = `${name} = ${rest.name}`;
result.push(rest);
if (children) {
getChildren(children, name, result);
}
});
}
const data = [{
name: "foo",
children: [{
count: 1,
name: "A"
},
{
count: 2,
name: "B"
}
]
},
{
name: "bar",
children: [{
count: 3,
name: "C",
children: [{
count: 4,
name: "D"
}]
}]
}
]
console.log(getTopChildren(data));

You can also do this recursively with flatMap based on whether or not a parent has been passed into the recursive call :
const data = [{
name: "foo",
children: [{
count: 1,
name: "A"
},
{
count: 2,
name: "B"
}
]
},
{
name: "bar",
children: [{
count: 3,
name: "C",
children: [{
count: 4,
name: "D"
}]
}]
}
];
function flatten(arr, parent = null) {
return parent
? arr.flatMap(({name, count, children}) => [
{name, count, label: `${parent} = ${name}`},
...flatten(children || [], parent)
])
: arr.flatMap(({name, children}) => flatten(children || [], name));
}
console.log(flatten(data));

Sometimes it's a little easier to reason about the code and write it clearly using generators. You can yield* from the recursive calls:
const data = [{name: "foo",children:[{count: 1,name: "A"},{ count: 2,name: "B"}]},{name: "bar",children: [{count: 3,name: "C",children: [{count: 4,name: "D"}]}]}]
function* flat(input, n){
if (!input) return
if (Array.isArray(input)) {
for (let item of input)
yield* flat(item, n)
}
let _name = n || input.name
if ('count' in input) {
yield { count:input.count, name:input.name, label:`${_name} = ${input.name}`}
}
yield* flat(input.children, _name)
}
let g = [...flat(data)]
console.log(g)
The function returns a generator, so you need to spread it into a list [...flat(data)] if you want a list or iterate over it if you don't need to store the list.

How to create a function to retrieve all children's id from a nested object

I want to retrieve all child ids of a specific group, which can be deeply nested or not.
Here is a sample json:
[
{
id: 1,
name: 'Desjardins Group 1',
children: [
{ id: 2, name: 'Analysts', children: [] },
{ id: 3, name: 'Administration', children: [] }
]
},
{
id: 4,
name: 'Desjardins Group 2',
children: [
{ id: 5, name: 'Consultants1', children: [] },
{
id: 6,
name: 'Consultant2',
children: [
{
id: 7, name: 'Interns', children: [
{ id: 8, name: 'subInterns1', children: [] },
{ id: 9, name: 'subInterns2', children: [] },
{ id: 10, name: 'subInterns3', children: [] }
]
}
]
}
]
}
]
I'm trying to make a function that takes an id has a parameter, and return all child ids.
Ex: getChildGroups(6) would return 7, 8, 9 and 10.
I guess recursive function and filters are the way to go, but i can't find a proper example.

Here's a simplified version of Johann Bauer's answer.
The first function just finds the first node that matches the given ID, with no need for any accumulation of data:
function findNode(data, id) {
if (!Array.isArray(data)) return;
for (let entry of data) {
if (entry.id === id) {
return entry;
} else {
const node = findNode(entry.children, id);
if (node) {
return node;
}
}
}
}
This second function just gets the child IDs, storing them in the passed array, without any intermediate arrays being created:
function getChildIds(node, result = []) {
if (!node) return;
if (!Array.isArray(node.children)) return;
for (let entry of node.children) {
result.push(entry.id);
getChildIds(entry, result);
}
return result;
}

It might be a good idea to split your problem into two smaller problems:
Find a group of ID x somewhere nested in the graph
Given a node, return all their sub-node IDs recursively
The solution to the first problem could look something like this:
function findGroupId(o, id) {
if (o.id == id) {
// We found it!
return o;
}
if (Array.isArray(o)) {
// If we start with a list of objects, pretend it is the root node
o = {children: o}
}
let results = [];
for (let c of o.children) {
// recursively call this function again
results.push(findGroupId(c, id))
}
// return the first matching node
return results.filter(r => r !== undefined)[0];
}
And for the second problem:
function getAllChildrenIDs(o) {
if (o.children === undefined)
return [];
let ids = [];
for (c of o.children) {
ids.push(c.id);
// recursively call this function again
for (id of getAllChildrenIDs(c))
ids.push(id);
}
return ids;
}
And if we put this together:
let example = [{
id: 1,
name: 'Desjardins Group 1',
children: [{
id: 2,
name: 'Analysts',
children: []
},
{
id: 3,
name: 'Administration',
children: []
}
]
},
{
id: 4,
name: 'Desjardins Group 2',
children: [{
id: 5,
name: 'Consultants1',
children: []
},
{
id: 6,
name: 'Consultant2',
children: [{
id: 7,
name: 'Interns',
children: [{
id: 8,
name: 'subInterns1',
children: []
},
{
id: 9,
name: 'subInterns2',
children: []
},
{
id: 10,
name: 'subInterns3',
children: []
}
]
}]
}
]
}
];
function findGroupId(o, id) {
if (o.id == id) {
return o;
}
if (Array.isArray(o)) {
o = {
children: o
}
}
let results = [];
for (let c of o.children) {
results.push(findGroupId(c, id))
}
return results.filter(r => r !== undefined)[0];
}
function getAllChildrenIDs(o) {
if (o.children === undefined)
return [];
let ids = [];
for (c of o.children) {
ids.push(c.id);
for (id of getAllChildrenIDs(c))
ids.push(id);
}
return ids;
}
console.log(getAllChildrenIDs(findGroupId(example, 6)))

Removing duplicate array values and then storing them [react]

I'm trying to strip the duplicate array values from my current array. And I'd like to store the fresh list (list without duplicates) into a new variable.
var names = ["Daniel","Lucas","Gwen","Henry","Jasper","Lucas","Daniel"];
const uniqueNames = [];
const namesArr = names.filter((val, id) => {
names.indexOf(val) == id; // this just returns true
});
How can I remove the duplicated names and place the non-duplicates into a new variable?
ie: uniqueNames would return...
["Daniel","Lucas","Gwen","Henry","Jasper"]
(I'm using react jsx) Thank you!

You can do it in a one-liner
const uniqueNames = Array.from(new Set(names));
// it will return a collection of unique items
Note that #Wild Widow pointed out one of your mistake - you did not use the return statement. (it sucks when we forget, but it happens!)
I will add to that that you code could be simplified and the callback could be more reusable if you take into account the third argument of the filter(a,b,c) function - where c is the array being traversed. With that said you could refactor your code as follow:
const uniqueNames = names.filter((val, id, array) => {
return array.indexOf(val) == id;
});
Also, you won't even need a return statement if you use es6
const uniqueNames = names.filter((val,id,array) => array.indexOf(val) == id);

If you want to remove duplicate values which contains same "id", You can use this.
const arr = [
{ id: 2, name: "sumit" },
{ id: 1, name: "amit" },
{ id: 3, name: "rahul" },
{ id: 4, name: "jay" },
{ id: 2, name: "ra one" },
{ id: 3, name: "alex" },
{ id: 1, name: "devid" },
{ id: 7, name: "sam" },
];
function getUnique(arr, index) {
const unique = arr
.map(e => e[index])
// store the keys of the unique objects
.map((e, i, final) => final.indexOf(e) === i && i)
// eliminate the dead keys & store unique objects
.filter(e => arr[e]).map(e => arr[e]);
return unique;
}
console.log(getUnique(arr,'id'))
Result :
[
{ id: 2, name: "sumit" },
{ id: 1, name: "amit" },
{ id: 3, name: "rahul" },
{ id: 4, name: "jay" },
{ id: 7, name: "sam" }
]

you forgot to use return statement in the filter call
const namesArr = duplicatesArray.filter(function(elem, pos) {
return duplicatesArray.indexOf(elem) == pos;
});

Since I found the code of #Infaz 's answer used somewhere and it confused me greatly, I thought I would share the refactored function.
function getUnique(array, key) {
if (typeof key !== 'function') {
const property = key;
key = function(item) { return item[property]; };
}
return Array.from(array.reduce(function(map, item) {
const k = key(item);
if (!map.has(k)) map.set(k, item);
return map;
}, new Map()).values());
}
// Example
const items = [
{ id: 2, name: "sumit" },
{ id: 1, name: "amit" },
{ id: 3, name: "rahul" },
{ id: 4, name: "jay" },
{ id: 2, name: "ra one" },
{ id: 3, name: "alex" },
{ id: 1, name: "devid" },
{ id: 7, name: "sam" },
];
console.log(getUnique(items, 'id'));
/*Output:
[
{ id: 2, name: "sumit" },
{ id: 1, name: "amit" },
{ id: 3, name: "rahul" },
{ id: 4, name: "jay" },
{ id: 7, name: "sam" }
]
*/

Also you can do this
{Array.from(new Set(yourArray.map((j) => j.location))).map((location) => (
<option value={`${location}`}>{location}</option>
))}