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Remove duplicate items from the array retracted from api

I am building a Blog app and I am trying to get results but it is showing duplicate results, I am trying to remove the duplicate results from the array.
But the problem is there are two key and values in each dict inside array, One is unique and other can be same so I am trying to distinct based on same array, It worked But the other key and value pair (which is unique) is not attaching with the other pair.
response which is returning from db
[
{
"id": 2,
"name": "user_1"
},
{
"id": 3,
"name": "user_3"
},
{
"id": 4,
"name": "user_3"
}
]
App.js
function App() {
const [blogs, setBlogs] = useState([]);
axios.get("retract_blogs/").then((res) => {
// Here I also want to attach "id"
setBlogs({[...new Set(res.data.data.map(x => x.name))]})
}
return(
<div>
{
blogs.map((user) =>
<div>
{user.name}
// Here I wamt to show ID
// {user.id}
</div>
}
</div>
)
}
I want to add id with x.username, I also tried using
setBlogs({data:[...new Set(res.data.data.map(x => x.name, x.id))]})
But it showed
x is not defined
But I am trying to add both name and id, and remove duplicates based on name not id.
I have tried many times but it is still not working.

To keep the id of the last occurence you can create a Map of the array keyed by name and then convert back to an array using the iterator returned by Map.values(). This works by overwriting earlier entries in the Map with the same name.
const users = [{ "id": 2, "name": "user_1" }, { "id": 3, "name": "user_3" }, { "id": 4, "name": "user_3" }];
const result = [...new Map(users.map((user) => [user.name, user])).values()];
console.log(result);
// [ { id: 2, name: 'user_1' }, { id: 4, name: 'user_3' } ]
If you instead want to keep the id of the first occurence of a name you can use a slightly modified 'group by' grouping into an object by name (here in a reduce() call, but it could easily be done in a standard loop as well) before taking the Object.values. This works by only setting the accumulator[name] property if it doesn't already exist, here using logical nullish assignment (??=)
const users = [{ "id": 2, "name": "user_1" }, { "id": 3, "name": "user_3" }, { "id": 4, "name": "user_3" }];
const result = Object.values(users.reduce((a, c) => (a[c.name] ??= c, a), {}));
console.log(result);
// [ { id: 2, name: 'user_1' }, { id: 3, name: 'user_3' } ]

Concatenate arrays from the same array in JavaScript

I have an array like this:
[
{
"id": 10002,
"flag": false,
"list": [
"aaa",
"bbb"
]
},
{
"id": 10001,
"flag": true,
"list": [
"10002",
"10003"
]
},
{
"id": 10003,
"flag": false,
"list": [
"ccc",
"ddd"
]
}
]
i tried this
initially i have "10001" value so iterate this array to take "list" array if flag==true then stored into newarray. but its not working.
I want it to be like this: [ "aaa", "bbb", "ccc", "ddd" ].

If i understand correctly this is what you want:
const someArray = [
{
"id": 10001,
"list": [
"10002",
"10003"
]
},
{
"id": 10002,
"list": [
"aaa",
"bbb"
]
},
{
"id": 10003,
"list": [
"ccc",
"ddd"
]
}
];
const [head,...rest] = someArray;
const result = head.list.reduce((acc,currentId)=>acc.concat(rest.find(({id})=> id === parseInt(currentId)).list),[]);
Here is a jsFiddle https://jsfiddle.net/sudakatux/9hju85mt/22/
Explanation:
take the head and splitted from the rest since the head contains the ids.
using the head as a dictionary find each list for each id in the head and concatenate
note the id must be in the subsequent list else it will fail with undefined. if you want to account for this error you can set a defualt empty object with a list. for example this part:
rest.find(({id})=> id === parseInt(currentId)).list
Will look like
rest.find(({id})=> id === parseInt(currentId)) || {list:[]}).list
Which basically means if its undefined return an object that has an empty list so then it will concatenate an empty list which results in being the same list. (like multiplying by 1 in a multiplication)
Hope it helps.
EDIT after your edit.
If your array is in different order you need to find the dictonary and then the logic is the same
const [newHead] = otherArray.filter(({list}) => list.every(elem=>!isNaN(elem)));
const result2 = newHead.list.reduce(
(acc,currentId) =>acc.concat(otherArray.find(({id})=> id === parseInt(currentId)).list),[]);
if you are testing for the flag then your head filter would look like. the blocks are the same the only thing that changes is the condition.
const [newHead] = otherArray.filter(({flag}) => flag));
(note* that instead of using the rest i used the complete array(otherArray). since im targeting equality.
Im using filter and extracting the first element of the result. because im accounting for the possibility that in the future you may have more than one "dictionary element". if thats the case in the future then you just have to concat the lists from the filter result

const array = [
{
id: 10001,
flag: true,
list: ["10002", "10003"]
},
{
flag: false,
id: 10002,
list: ["aaa", "bbb"]
},
{
flag: false,
id: 10003,
list: ["ccc", "ddd"]
}
];
const isHead = item => item.flag && item.id === 10001;
const head = array.find(isHead);
const rest = array.filter(item => !isHead(item));
const result = rest
.flatMap(item =>
head.list.includes(item.id.toString()) && item.list
);
console.log(result);

You can map over the list of the first item and concat all the lists from those ids.
const mapItems = (input) => {
const source = input[0].list;
source.reduce((results, id) => {
return results.concat(input.find(item => item.id === id).list);
}, []);
};
mapItems([
{
"id": 10001,
"list": [
"10002",
"10003"
]
},
{
"id": 10002,
"list": [
"aaa",
"bbb"
]
},
{
"id": 10003,
"list": [
"ccc",
"ddd"
]
}
]);

You can fetch the values of the list of first object in the array as arr[0]['list']
Once you have these values (10002,10003) then you can fetch the list values of remaining objects in the array whose id key matches one of the above values.
if(arr[i]['id'] == 10002 || arr[i]['id'] == 10003){
//fetch the list values
}

converting array to object while considering keys of the same value

I am trying to figure out an easy way to convert an array of objects to an object
I have an array of objects that looks like this:
[
{
"id": "-LP9_kAbqnsQwXq0oGDT",
"value": Object {
"date": 1541482236000,
"title": "First",
},
},
.... more objects here
]
And id like to convert it to an object with the timestamps as the keys, and arrays of objects corresponding to that date. If that key already exists, then add the object to the corresponding array associated with that key
{
1541482236000:
[{
"id": "-LP9_kAbqnsQwXq0oGDT",
"value": Object {
"date": 1541482236000,
"title": "First",
},
},
{
"id": "-LP9_kAbqnsQwXqZZZZ",
"value": Object {
"date": 1541482236000,
"title": "Some other title",
},
},
.... more objects here
],
1541482236001:
[{
"id": "-LP9_kAbqnsQ1234",
"value": Object {
"date": 1541482236001,
"title": "Another title",
},
},
.... more objects here
]
}
I was able to achieve something similar using reduce. However it does not handle adding objects to the array when their key already exists.
calendarReminders = action.value.reduce((obj, reminder) => {
dateKey = moment(reminder.value.date).format('YYYY-MM-DD')
obj[dateKey] = [reminder]
return obj;
}, {});
How can I do this?

You just need to check whether the object is already a key and if not add it with the value of an array. Then you can just push() into it:
let arr = [{"id": "-LP9_kAbqnsQwXq0oGDT","value": {"date": 1541482236000,"title": "First",},},{"id": "SomID","value": {"date": 1541482236000,"title": "Some other title",},},{"id": "A different ID","value": {"date": 1541482236001,"title": "A third title",},}]
let calendarReminders = arr.reduce((obj, reminder) => {
(obj[reminder.value.date] || (obj[reminder.value.date] = [])).push(reminder)
return obj;
}, {});
console.log(calendarReminders)
If you want to set the keys to a different format with moment, you should be able to do that without changing the basic idea.

Please test the below code!
First you iterate through your array of data,
if your result object/dictionary already has the key then you just add the current item
otherwise you make the key and set the value
const data = [];
let result = {};
for (const item of data) {
const key = item.value.date;
if (result.hasOwnProperty(key)) {
const prevData = result[key];
result[key] = [...prevData, item];
} else {
result[key] = [item];
}
}

update/merge array values in React Redux store correctly without duplicates

My initial state is like below and if new Book added or price is changed then new updated array is coming from service whose result i need to merge in my initial state.
const initialState = {
booksData: [
{"Code":"BK01","price":"5"},
{"code":"BK02","price":"30"},
{"code":"BK03","price":"332"},
{"code":"BK04","price":"123"}
]
};
Updated array from server with few records updated/new
data: [
{"Code":"BK01","price":"10"},
{"code":"BK02","price":"25"},
{"code":"BK05","price":"100"}
]
updated state should become after merging updated array with old array.
booksData: [
{"Code":"BK01","price":"10"},
{"code":"BK02","price":"25"},
{"code":"BK03","price":"332"},
{"code":"BK04","price":"123"},
{"code":"BK05","price":"100"}
]

I would filter out elements of the old data that are in the new data, and concat.
const oldBooks = booksData.filter(book => !newData.some(newBook => newBook.code === book.code));
return oldBooks.concat(newData);
Keep in mind you must NOT push values into the old array. In your reducer you MUST create new instances, here a new array. 'concat' does that.

You can first merge both the array together and then reduce it to remove duplicates like
var booksData = [
{"code":"BK01","price":"5"},
{"code":"BK02","price":"30"},
{"code":"BK03","price":"332"},
{"code":"BK04","price":"123"}
]
var newData = [
{"code":"BK01","price":"10"},
{"code":"BK02","price":"25"},
{"code":"BK05","price":"100"}
]
const result = [...newData, ...booksData].reduce((res, data, index, arr) => {
if (res.findIndex(book => book.code === data.code ) < 0) {
res.push(data);
}
return res;
}, [])
console.log(result);

Merge the two array and filter using 'Code' property
const initialState = {
booksData: [
{ "Code": "BK01", "price": "5" },
{ "code": "BK02", "price": "30" },
{ "code": "BK03", "price": "332" },
{ "code": "BK04", "price": "123" }
]
};
const data =
[
{ "Code": "BK01", "price": "10" },
{ "code": "BK02", "price": "25" },
{ "code": "BK05", "price": "100" }
]
let newState = [...initialState.booksData, ...data];
newState = newState.filter((obj, pos, arr) => {
return arr.map(mapObj => mapObj['Code']).indexOf(obj['Code']) !== pos;
});
console.log(newState);

Collection of Objects
Filter a merged array to pick only non-existent items by iterating every item in the merged array which its index is before the current index of the "parent" filter iterator
const mergedUnique = [
...[{id:1}, {id:2}, {id:3}],
...[{id:1}, {id:4}, {id:2}]
]
.filter((item, idx, arr) =>
!arr.some(({id}, subIdx) => subIdx < idx && id == item.id)
)
console.log( mergedUnique )
Basic technique for "simple" arrays
Merge some arrays and filter them to pick only non-existent items by checking if the same item exists anywhere before the current item's index in the merged array.
lastIndexOf is used to check backwards, if the current value exists already, which contributes to keeping the order of the merged array in a certain way which might be desirable, which can only be achieved by checking backward and not forward.
Skip checking the first item - is obviously not a duplicate.
const mergedUniqe = [...[1,2,3], ...[1,3,4,5,2]] // [1, 2, 3, 1, 3, 4, 5, 2]
.filter((item, idx, arr) =>
!~arr.lastIndexOf(item, idx-1) || !idx
)
console.log( mergedUniqe )

Merge Arrays Combining Matching Objects in Angular Javascript

I have 2 array objects in Angular JS that I wish to merge (overlap/combine) the matching ones.
For example, the Array 1 is like this:
[
{"id":1,"name":"Adam"},
{"id":2,"name":"Smith"},
{"id":3,"name":"Eve"},
{"id":4,"name":"Gary"},
]
Array 2 is like this:
[
{"id":1,"name":"Adam", "checked":true},
{"id":3,"name":"Eve", "checked":true},
]
I want the resulting array after merging to become this:
[
{"id":1,"name":"Adam", "checked":true},
{"id":2,"name":"Smith"},
{"id":3,"name":"Eve", "checked":true},
{"id":4,"name":"Gary"},
]
Is that possible? I have tried angular's array_merge and array_extend like this:
angular.merge([], $scope.array1, $scope.array2);
angular.extend([], $scope.array1, $scope.array2);
But the above method overlap the first 2 objects in array and doesn't merge them based on matching data. Is having a foreach loop the only solution for this?
Can someone guide me here please?

Not sure if this find of merge is supported by AngularJS. I've made a snippet which does exactly the same:
function merge(array1, array2) {
var ids = [];
var merge_obj = [];
array1.map(function(ele) {
if (!(ids.indexOf(ele.id) > -1)) {
ids.push(ele.id);
merge_obj.push(ele);
}
});
array2.map(function(ele) {
var index = ids.indexOf(ele.id);
if (!( index > -1)) {
ids.push(ele.id);
merge_obj.push(ele);
}else{
merge_obj[index] = ele;
}
});
console.log(merge_obj);
}
var array1 = [{
"id": 1,
"name": "Adam"
}, {
"id": 2,
"name": "Smith"
}, {
"id": 3,
"name": "Eve"
}, {
"id": 4,
"name": "Gary"
}, ]
var array2 = [{
"id": 1,
"name": "Adam",
"checked": true
}, {
"id": 3,
"name": "Eve",
"checked": true
}, ];
merge(array1, array2);

Genuinely, extend in Angular works with object instead of array. But we can do small trick in your case. Here is another solution.
// a1, a2 is your arrays
// This is to convert array to object with key is id and value is the array item itself
var a1_ = a1.reduce(function(obj, value) {
obj[value.id] = value;
return obj;
}, {});
var a2_ = a2.reduce(function(obj, value) {
obj[value.id] = value;
return obj;
}, {});
// Then use extend with those two converted objects
var result = angular.extend([], a1_, a2_).splice(1)
Notes:
For compatibility, reduce may not work.
The after array will replace the previous one. This is because of implementation of extend in Angular.