Is there an efficient way of creating a new array from 2 arrays?
var employees1 = [
{ id: 11, name: 'joe' },
{ id: 12, name: 'mike' },
{ id: 13, name: 'mary' },
{ id: 14, name: 'anne' }
];
var employees2 = [
{ id: 11, message: 'test1' },
{ id: 12, message: 'test2' },
{ id: 13, message: 'test3' },
{ id: 14, message: 'test4' }
];
Iterate employees1 array and get 'message' for matching id from employees2. Resulting in new array:
var employees3 = [
{ id: 11, name: 'joe', message: 'test1' },
{ id: 12, name: 'mike', message: 'test2' },
{ id: 13, name: 'mary', message: 'test3' },
{ id: 14, name: 'anne', message: 'test4' }
];
Is this possible using Map function? Or using a standard foreach suggested?
Iterate over the first array, search for the element in the second array and finally push them to the new array as illustrated below:
var employees3 = [];
employees1.forEach(emp1 => {
const findEmp = employees2.find(emp2 => emp2.id === emp1.id);
if (findEmp) {
employees3.push({
...emp1,
...findEmp
});
}
});
console.log(employees3);
You can use Array#map and Array#find to get the desired output. I am attaching a sample code:
var employees3 = employees1.map(emp => ({
...emp,
...(employees2.find(item => item.id === emp.id) ?? {})
}))
Related
var arr = [
{ id: 1, name: 'Ahmed Malick', school: 'TEWGS' },
{ id: 2, name: 'Tehmeed Anwar', school: 'DGS' },
{ id: 3, name: 'Azhar Yameen', school: 'DGS' }
]
I want this output:
The student name is his id is and he studies in
Can you please show me what kind of output you expect. Then i will try to solve it.
I'm not sure if this is what you want
var arr = [
{ id: 1, name: "Ahmed Malick", school: "TEWGS" },
{ id: 2, name: "Tehmeed Anwar", school: "DGS" },
{ id: 3, name: "Azhar Yameen", school: "DGS" },
];
arr.map((student) => {
return `Name: ${student.name}, id: ${student.id}, he studies in: ${student.school}`;
}).forEach((output) => {
console.log(output);
});
If you want it in the DOM do this
let html = arr.map((student) => {
return `<p><strong>Name</strong>: ${student.name}, <strong>id</strong>: ${student.id},<strong> he studies in</strong> ${student.school}</p>`;
}).join("")
document.createElement("div").innerHTML = html
Try thatGood luck
Given two arrays, farmers and collections, I want to be able to merge the farmer information to each collection when farmer_id in the collection is equal to id in farmers. if there is no id of the farmer that matches farmer_id in the collection then that collection should have a an empty farmer object
const farmers = [{
id: 10,
name: 'John Doe',
email: 'jdoe#gmail.com'
},
{
id: 11,
name: 'James Bond',
email: 'james#gmail.com'
}
]
const collections = [{
id: 9,
name: 'Book',
farmer_id: 10,
date: 'June'
},
{
id: 10,
name: 'Game',
farmer_id: 11,
date: 'July'
},
{
id: 13,
name: 'Car',
farmer_id: 10,
date: 'August'
},
{
id: 11,
name: 'Wristwatches',
farmer_id: 20,
date: 'August'
}
]
The result should be in this format below
const result = [{
id: 9,
name: 'Book',
farmer_id: 10,
date: 'June',
farmer: {
id: 10,
name: 'John Doe',
email: 'jdoe#gmail.com'
}
},
{
id: 10,
name: 'Game',
farmer_id: 11,
date: 'July',
farmer: {
id: 11,
name: 'James Bond',
email: 'james#gmail.com'
}
},
{
id: 13,
name: 'Car',
farmer_id: 10,
date: 'August',
farmer: {
id: 10,
name: 'John Doe',
email: 'jdoe#gmail.com'
}
},
{
id: 11,
name: 'Wristwatches',
farmer_id: 20,
date: 'August',
farmer: {}
}
]
This is what i have been able to come up with but am stuck right now
function mapper(farmers, collectors) {
for (let k = 0; k < farmers.length; k++) {
const idToFarmerInfo = {};
idToFarmerInfo[farmers[k].id] = farmers[k];
for (let j = 0; j < collectors.length; j++) {
let mapper = idToFarmerInfo[collectors[j].farmer_id];
farmers[mapper] = collectors[j]
}
}
return farmers
}
i followed this link as am trying to avoid O of N squared but O of N complexity
For a better performance you could create a hash of farmers where the complexity is O(N) because we're iterating the farmers list only once.
const farmers = [{ id: 10, name: 'John Doe', email: 'jdoe#gmail.com' }, { id: 11, name: 'James Bond', email: 'james#gmail.com' } ]; const collections = [{ id: 9, name: 'Book', farmer_id: 10, date: 'June' }, { id: 10, name: 'Game', farmer_id: 11, date: 'July' }, { id: 13, name: 'Car', farmer_id: 10, date: 'August' }, { id: 11, name: 'Wristwatches', farmer_id: 20, date: 'August' } ]
var farmers_hash = farmers.reduce((hash, item) => {
hash[item.id] = item;
return hash;
}, {});
console.log(farmers_hash);
The following step is to build the desired output by assigning one farmer using hash keys.
This can be achieved using map method in combination with Object.assign.
const farmers = [{ id: 10, name: 'John Doe', email: 'jdoe#gmail.com' }, { id: 11, name: 'James Bond', email: 'james#gmail.com' } ]; const collections = [{ id: 9, name: 'Book', farmer_id: 10, date: 'June' }, { id: 10, name: 'Game', farmer_id: 11, date: 'July' }, { id: 13, name: 'Car', farmer_id: 10, date: 'August' }, { id: 11, name: 'Wristwatches', farmer_id: 20, date: 'August' } ]
var farmers_hash = farmers.reduce((hash, item) => {
hash[item.id] = item;
return hash;
}, {});
var result = collections.map((item) => {
item.farmer = Object.assign({}, farmers_hash[item.farmer_id])
return item;
});
console.log(result);
As you can see the final complexity is O(N) + O(M) where N is the length of farmers array and M is the length of collections array.
Demo on stackblitz
You can use a more declarative approach and use Array.map and Array.find
const result = collections.map(collection => {
return {
...collection,
farmer: farmers.find(farmer => collection.farmer_id == farmer.id) || {}
};
});
console.log(result);
You can create a Map collection to have O(N) of access to desired farmer by id. Then mapping becomes faster in terms of performance:
const unique = new Map(farmers.map(f=> [f.id, f]));
const result = collections.map(s => ({
...s, farmer_id: unique.get(s.farmer_id) || s.farmer_id
}))
Now mapping of collections has complexity O(N). However, do not forget to sum complexity of making unique farmers. The overall complexity is O(N) + O(M).
An example:
const farmers = [{
id: 10,
name: 'John Doe',
email: 'jdoe#gmail.com'
},
{
id: 11,
name: 'James Bond',
email: 'james#gmail.com'
}
];
const collections = [{
id: 9,
name: 'Book',
farmer_id: 10,
date: 'June'
},
{
id: 10,
name: 'Game',
farmer_id: 11,
date: 'July'
},
{
id: 13,
name: 'Car',
farmer_id: 10,
date: 'August'
},
{
id: 11,
name: 'Wristwatches',
farmer_id: 20,
date: 'August'
}
];
const unique = new Map(farmers.map(f=> [f.id, f]));
const result = collections.map(s => ({
...s, farmer_id: unique.get(s.farmer_id) || s.farmer_id
}))
console.log(result);
I have a object array in which each object contain an id and a name and a separate array contains a set of ids. I want to filter first array based on the second array.
const data= [
{
id: 1,
name: 'name1'
},
{
id: 2,
name: 'name2'
},
{
id: 3,
name: 'name3'
},
{
id: 4,
name: 'name4'
}
];
const array = [1,3,4];
const expectedResult= [
{
id: 1,
name: 'name1'
},
{
id: 3,
name: 'name3'
},
{
id: 4,
name: 'name4'
}
];
Use .filter and .includes
const data= [
{
id: 1,
name: 'name1'
},
{
id: 2,
name: 'name2'
},
{
id: 3,
name: 'name3'
},
{
id: 4,
name: 'name4'
}
];
const array = [1, 3, 4]
const result = data.filter((item) => {
//gives us items that passes a condition
return array.includes(item.id)
})
console.log(result)
i have multiple data for one id , i want filter my data like this
$scope.mpArray =[
{ Id: 1, Name: Madhu, Address: Upal },
{ Id: 1, Name: Chandu, Address: Upal },
{ Id: 2, Name: Srinu, Address: Kphb },
{ Id: 2, Name: Vijay, Address: kphb },
{ Id: 3, Name: Ajay, Address: Banglore },
{ Id: 3, Name: Narsi, Address: Banglore },
{ Id: 3, Name: Peter, Address: Banglore },
];
i want to filter my array like this
var FilterArray = [
{ Id: 1,Madhu, Chandu},
{ Id: 2, Srinu, Vijay},
{ Id: 3, Ajay, Narsi, Peter},
];
At first you need to change your FilterArray to
[
{
"Id": 1,
"Name": [
"Madhu",
"Chandu"
]
},
{
"Id": 2,
"Name": [
"Srinu",
"Vijay"
]
},
{
"Id": 3,
"Name": [
"Ajay",
"Narsi",
"Peter"
]
}
]
Notice that name is an array. The FilterArray of your question
var FilterArray = [
{ Id: 1,Madhu, Chandu},
{ Id: 2, Srinu, Vijay},
{ Id: 3, Ajay, Narsi, Peter},
];
Do not contain a valid JSON object inside the array so you need to change the structure to the one where add a new key Name in the JSON object of FilterArray as like the first structure above. Then the below code works great.
$(document).ready(function(){
var myArray =[
{ Id: 1, Name: "Madhu", Address: "Upal" },
{ Id: 1, Name: "Chandu", Address: "Upal" },
{ Id: 2, Name: "Srinu", Address: "Kphb" },
{ Id: 2, Name: "Vijay", Address: "kphb" },
{ Id: 3, Name: "Ajay", Address: "Banglore" },
{ Id: 3, Name: "Narsi", Address: "Banglore" },
{ Id: 3, Name: "Peter", Address: "Banglore" },
];
var FilterArray = [];
var matched;
for(var i=0;i<myArray.length; i++){
matched = false;
var myArrayId = myArray[i].Id;
for(var j=0; j<FilterArray.length; j++){
var FilterArrayId = FilterArray[j].Id;
if(myArrayId === FilterArrayId){
matched = true;
FilterArray[j].Name.push(myArray[i].Name);
// no need to loop further
break;
}
}
if(!matched){
var obj = {
'Id' : myArrayId,
'Name' : [myArray[i].Name],
}
FilterArray.push(obj);
}
}
console.log(FilterArray);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
try this
var mpArray =[
{ Id: 1, Name: 'Madhu', Address: 'Upal' },
{ Id: 1, Name: 'Chandu', Address: 'Upal' },
{ Id: 2, Name: 'Srinu', Address: 'Kphb' },
{ Id: 2, Name: 'Vijay', Address: 'kphb' },
{ Id: 3, Name: 'Ajay', Address: 'Banglore' },
{ Id: 3, Name: 'Narsi', Address: 'Banglore' },
{ Id: 3, Name: 'Peter', Address: 'Banglore' },
];
var filterObject = {};
mpArray.forEach(function (item) {
if (!filterObject[item.Id]) {
filterObject[item.Id] = [];
}
filterObject[item.Id].push(item.Name);
});
console.log(filterObject);
$scope.mpArray =[
{ Id: 1, Name: 'Madhu', Address: 'Upal' },
{ Id: 1, Name: 'Chandu', Address: 'Upal' },
{ Id: 2, Name: 'Srinu', Address: 'Kphb' },
{ Id: 2, Name: 'Vijay', Address: 'kphb' },
{ Id: 3, Name: 'Ajay', Address: 'Banglore' },
{ Id: 3, Name: 'Narsi', Address: 'Banglore' },
{ Id: 3, Name: 'Peter', Address: 'Banglore' },
];
var FilterArray = [];
var FilteredArrayIds=[];
$scope.mpArray.forEach(
function(detailObj) {
if(FilteredArrayIds.indexOf(detailObj.Id)==-1)
return FilteredArrayIds.push(detailObj.Id);
});
for(var i=0; i<FilteredArrayIds.length;i++)
{
var result = $scope.mpArray.filter(function( obj ) {
return obj.Id == FilteredArrayIds[i];
});
var rsltNames = result.map(function(obj){
return obj.Name;
})
var filteredObj ={
id:FilteredArrayIds[i]+',' +rsltNames.join()
}
FilterArray.push(filteredObj);
}
console.log(filteredObj)
I have the following simple JSON array:
const personList = [
{
id: 1,
name: "Phil"
},
{
id: 2,
name: "Bren"
},
{
id: 3,
name: "Francis Underwood"
},
{
id: 4,
name: "Claire Underwood"
},
{
id: 5,
name: "Ricky Underwood"
},
{
id: 6,
name: "Leo Boykewich"
}
];
And I would like to filter this by passing an array of ids so something like [1,4] would be passed in and it would only return "Phill" and "Claire Underwood"
This is what the function looks like but I know it's wrong attendeeIds is an array that's passed in [1, 4]:
getAttendeesForEvent: (attendeeIds) => {
if (attendeeIds === undefined) return Promise.reject("No attendee id provided");
return Promise.resolve(personList.filter(x => x.id == [attendeeIds]).shift());
}
I haven't used JS in years. I've looked for examples but they all seem too complex for what I'm trying to achieve. So how can I filter this based on an array of id's passed in?
return Promise.resolve(personList.filter(x => attendeeIds.indexOf(x.id) !== -1));
You want to check if the id of each item your looping over exists inside of attendeeIds. Use Array.indexOf inside of the filter to do that.
This will return an array of { id: #, name: String } objects.
If you want to return just the names of those objects, you can do a map afterwards which will transform an array into another array using the function that you provide.
const filteredNames = personList
.filter(x => attendeeIds.indexOf(x.id) !== -1)
.map(x => x.name);
// ['Phil', 'Claire Underwood']
You could do something in these lines. Hope this helps.
const personList = [{
id: 1,
name: "Phil"
}, {
id: 2,
name: "Bren"
}, {
id: 3,
name: "Francis Underwood"
}, {
id: 4,
name: "Claire Underwood"
}, {
id: 5,
name: "Ricky Underwood"
}, {
id: 6,
name: "Leo Boykewich"
}];
let attendeeIds = [1, 5];
let getAttendeesForEvent = () => {
return new Promise(function(resolve, reject) {
if (attendeeIds === undefined) {
reject("No attendee id provided");
} else {
resolve(personList.filter((x) => attendeeIds.includes(x.id)).map((obj) => obj.name));
}
});
}
getAttendeesForEvent().then((data) => console.log(data))