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' } ]
Related
I have a Javascript question related to mapping. So I have two arrays...
Array1
[
{
"id": 1,
"name": "admin"
},
{
"id": 2,
"name": "analyst"
},
{
"id": 3,
"name": "reviewer"
},
{
"id": 4,
"name": "administrator"
},
{
"id": 5,
"name": "leader"
}
]
Array2
[ false, false, false, false, false]
I want to create a third array. So I create a variable and set its initial value to be empty.
const roles = [];
What I want to do is include the objects in Array1 into roles based on the boolean values in Array2 in sequential order.
For example, if Array2 looks like [true, false, true, false, false], then roles would be this...
roles = [
{
"id": 1,
"name": "admin"
},
{
"id": 3,
"name": "reviewer"
},
]
The reason is because the first and third boolean values in Array2 are true, therefore it takes the first and third objects in Array1 and puts them into roles
I know that either .map or .forEach is the solution here, but I don't quite know the best approach.
Can anyone assist?
UPDATE
I got this error
Element implicitly has an 'any' type because expression of type 'number' can't be used to index type 'FormArray'.
No index signature with a parameter of type 'number' was found on type 'FormArray'.
const roles = this.listOfRoles.filter((item, index) => this.rolesArray[index]).map((filtered) => ({ id: filtered.id }));
Thanks!
You can filter array one and return value based on array 2 to filter out data like below :-
const roles = array1.filter((item, index) => array2[index]);
Answer to 2nd query from comment, if you just want to return id :-
const roles = array1.filter((item, index) => array2[index]).map((filtered) => ({id: filtered.id}));
I am hitting an endpoint that is returning an array of objects, each object can potentially have a set of fields, e.g.,
const FIELDS = [
'id',
'title',
'contributor',
'mediatype',
'source'
]
However, some objects will only have some of those fields, some may have all.
const items = [
{
"id": 1,
"title": "some title 1",
"contributor": "bob",
"mediatype": "text"
},
{
"id": 2,
"title": "some title 2",
"mediatype": "text"
}.
{
"id": 3,
"title": "some title 3",
"mediatype": "movies"
"source": "comcast"
}
]
I want to "normalize" all the objects such that every single one contains every expected field, filling the "gaps" with null, or some falsey value such that graphql (which I intend to eventually feed it into) is happy.
const items = [
{
"id": 1,
"title": "some title 1",
"contributor": "bob",
"mediatype": "text",
"source": null
},
{
"id": 2,
"title": "some title 2",
"mediatype": "text",
"contributor": null,
"source": null
}.
{
"id": 3,
"title": "some title 3",
"mediatype": "movies",
"contributor": null,
"source": "comcast"
}
]
My "nasty" looking code looks something like this
const normalize = items =>
items.map(item => {
FIELDS.forEach(f => {
if (!item[f]) {
item[f] = null;
}
});
return item;
});
Any suggestions for writing this more elegantly - either with vanilla JS or lodash, which I am equally open to using as its already available in my codebase?
You can use spread syntax, but then it would be better to define FIELDS as a template object:
const FIELDS = {
id: null,
title: null,
contributor: null,
mediatype: null,
source: null
};
const normalize = items => items.map(item => ({...FIELDS, ...item}));
Your if (!item[f]) test will match on any falsy value, which is probably not what you want.
Instead, you should properly check if the key exists, e.g.:
if (!(f in item))
Not sure if this is any better really... but here is some equivalent alternative syntax.
Use an "equals itself or null" to squeeze out a bit more sugar:
const normalize = items =>
items.map(item => {
FIELDS.forEach(f => item[f] = item[f] || null);
return item;
});
Or test everyone's patience with this one liner:
const normalize = items =>
items.map(item => FIELDS.reduce((acc, field) => {acc[field] = item[field] || null; return acc}, item));
The choice is yours.
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
}
How can I get the new object added to an array after componentDidUpdate?
I have this two objects in prevProps:
objArray1 = [
{
"id": 1,
"name": "abc",
},
{
"id": 2,
"name": "def",
}
]
and I get this three objects in this.props
objArray2 = [
{
"id": 1,
"name": "abc",
},
{
"id": 2,
"name": "def",
},
{
"id": 3,
"name": "ghi",
}
]
and I want to get at the object that changed
newObject ={
"id": 3,
"name": "ghi",
}
so that I can pass it to another function
Create a Set of id values from the prevProps with Array.map(), and filter out the new props that has an id that exists in the Set:
const prevProps = [{"id":1,"name":"abc"},{"id":2,"name":"def"}]
const props = [{"id":1,"name":"abc"},{"id":2,"name":"def"},{"id":3,"name":"ghi"}]
const prevSet = new Set(prevProps.map(o => o.id))
const added = props.filter(o => !prevSet.has(o.id))
console.log(added)
If new items are always added to the end of the array, you can use Array.slice() to remove the previous items (the length of `prevProps), and get the new items:
const prevProps = [{"id":1,"name":"abc"},{"id":2,"name":"def"}]
const props = [{"id":1,"name":"abc"},{"id":2,"name":"def"},{"id":3,"name":"ghi"}]
const added = props.slice(prevProps.length)
console.log(added)
You can filter objArray2 with id
objArray2.filter(ele=> !objArray1.some(value=> value.id === ele.id) )
If extra items are always added after the previous object you can slice
objArray2.slice(objArray1.length,)
if the IDs increment by one each time they're added. Then you could store the latest id and check for greater ones on update.
I am trying to use Lodash to filter an array of objects based on a match of id's, this is what I have tried:
var team = _.find(this.teams, { 'id': this.newSchedule.team});
_.filter(this.yards, function(yard) {
return _.find(team.yards, { id: yard.id });
});
yards data:
[ { "id": 1, "name": "Test" },{ "id": 2, "name": "Test 2" } ]
team data:
[ { "id": 1, "name": "Team 1", "yards": [{ "id": 1, "name" }] ]
I want this.yards to show the yards based on the yard id from a selected team.
Its hard to understand what you mean, does the yard id match the team id?
If so it sounds like what you need to do is first find the team with the same id then grab that teams yards. Therefore I would use the map function twice:
const result = this
.yards
.map(y => team.find(t => t.id === y.id)) // join with the right team
.map(t => t.yards) // reduce to that teams yards
As team is an array, you need to iterate it before doing the _.find on an individual element in that array. It doesn't help that you called your variable team (singular). teams would make more sense.
Here is how you would change your lodash code:
var yards = [ { id: 1, name: "Test" },{ id: 2, name: "Test 2" } ],
teams = [ { id: 1, name: "Team 1", yards: [{ id: 1, name: "Missing string" }] } ]
result = _.filter(this.yards, function(yard) {
return _.some(this.teams, function(team) {
return _.find(team.yards, { id: yard.id });
});
});
console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js"></script>
So this returns the yards that are related to at least one team.