If given an array of ids [1,2,3,4,5]
And an object array:
[{animal:tiger, id:1}, {animal:"fish", id:2}]
What would be the suggested way to return 'tiger, fish'. Would that be through using .map or would a for loop be better for constructing the sentence?
What you need is just go through the list of ids and find corresponding animal in the animals list.
Note, that in case animals list is not expected to store all the animals and some of them are missing, you will need to add additional filter step to be sure that no undefined values appear on the last map step.
const ids = [1,5,2,4,3,6]; // added 6 which is missing in animals
const animals = [
{name:'Tiger',id:1},
{name:'Horse',id:2},
{name:'Mouse',id:3},
{name:'Elephant',id:4},
{name:'Cat',id:5}
];
const result = ids
.map(id => animals.find(a => a.id === id))
.filter(Boolean) // this will exclude undefined
.map(a => a.name)
.join(',');
console.log(result);
var ids = [1,2,3,4,5];
var objects = [{ animal:"tiger", id: 1 }, { animal: "fish", id: 2 }];
objects.map(function(o) { if(ids.includes(o.id)) return o.animal }).join();
I'm guessing you only want the animal names who's id appears in your array. If so, you could filter the array of objects first, followed by a map and a join.
let idarr = [1, 2, 3, 4];
let objarr = [{
animal: "tiger",
id: 1
}, {
animal: "fish",
id: 2
}];
console.log(objarr.filter(x => idarr.includes(x.id)).map(x => x.animal).join(', '))
I suggest two options, depending on your data & use cases.
1. map + find if the animal kingdoms are not too many to loop through.
const animals = [
{animal:tiger, id:1},
{animal:"fish", id:2}
]
const ids = [1,2,3,4,5];
const names = ids.map(id =>
animals.find(animal => animal.id === id));
2. convert animals array to object first, for easier frequent access later. One upfront loop, then easier to access by id later.
const animals = [
{animal: "tiger", id:1},
{animal: "fish", id:2}
]
/*
Convert
[{animal:tiger, id:1}, {animal:"fish", id:2}]
to
{
1: { animal: "tiger", id: 1 },
2: { animal: "fish", id: 2 },
}
*/
const animalsObj = animals.reduce((acc, animal) => {
return {
...acc,
[animal.id]: animal,
}
}, {});
const ids = [1,2,3,4,5];
const names = ids.map(id => animalsObj[id].animal)
Related
I have a JSON response as below:
[{
"id": 1,
"food": {
"fruits": ["Banana", "Orange", "Apple", "Mango"],
"veggies": ["greens", "peppers", "carrot", "potatoes"],
}
},
{
"id": 2,
"food": {
"fruits": ["grapes", "berries", "peach", "pears"],
"veggies": ["cabbage", "spinach"],
"dairy": ["nutmilk", "goatmilk"]
}
}
]
Now i want to merge the Arrays each "id" (1,2 in example) into string ( ; delimited) like below:
id_1 = Banana;Orange;Apple;Mango;greens;peppers;carrot;potatoes
// observer "id_2" has additional array - "dairy"
id_2 = grapes;berries;peach;pears;cabbage;spinach;nutmilk;goatmilk
The key's are dynamic so for some records there are 2 arrays and for some records it can be 3 or 4 and may be 1.
I tried using react/Java Script Array.concat(), but i am not sure how to do it dynamically. Please help me. Thank you.
This is doable easily using Object.values().flat().join(';') demonstrated below:
let arr=[{"id":1,"food":{"fruits":["Banana","Orange","Apple","Mango"],"veggies":["greens","peppers","carrot","potatoes"],}},{"id":2,"food":{"fruits":["grapes","berries","peach","pears"],"veggies":["cabbage","spinach"],"dairy":["nutmilk","goatmilk"]}}];
const result = arr.map(({id,food}) => ({id, food: Object.values(food).flat().join(';')}));
console.log(result);
You may easily restructure the output by simply changing it to e.g. ["id_"+id]: Object.values(...)
First flatten using map, flat and join. Then convert the resulting array of objects to a single object using assign.
var db = [{"id": 1,"food": {"fruits": ["Banana", "Orange", "Apple", "Mango"], "veggies": ["greens","peppers","carrot","potatoes"], }},{"id" : 2,"food": {"fruits": ["grapes", "berries", "peach", "pears" ], "veggies": ["cabbage","spinach"], "dairy": ["nutmilk","goatmilk"]}}];
var flat = db.map(
({id, food}) => ({[`id_${id}`]: Object.values(food).flat().join(';')})
);
var result = Object.assign(...flat);
console.log(result);
This is really two problems: looping through an array of objects to combine them into one object, and looping through an object to concat all of its array.
Tackling the second one first, something like this would work:
const concatArraysInObject = obj =>
Object.values(obj).reduce((result, arr) => result.concat(arr), []);
const input = { a: [1,2,3], b: [4,5,6], c: [7,8,9] };
const output = concatArraysInObject(input);
console.log(output);
Object.values() will give you an array of all arrays in an object.
The reduce() function takes a two parameters: a function and initial value.
The function should also take (at least) 2 parameters: the result of the last call (or initial value) and the current value in the array.
It'll call the function once for each element in the array.
Now, with that solved, we can tackle the first problem.
For this, we can also use reduce() as well, and we'll construct our combined object on each call.
const concatArraysInObject = (obj) =>
Object.values(obj).reduce((result, arr) => result.concat(arr), []);
const mergeObjectsInArray = (arr, dataKey) =>
arr.reduce((result, obj) => ({ ...result, [obj.id]: concatArraysInObject(obj[dataKey]) }), {});
const input = [
{ id: 'A', data: { a: [1,2,3], b: [4,5,6] } },
{ id: 'B', data: { c: [7,8,9], d: [10,11,12] } }
];
const output = mergeObjectsInArray(input, 'data');
console.log(output);
An important note of warning: object key order is NOT guaranteed in JavaScript. While 99% of the time they will be in the order you expect, this is not a guarantee, so if you depend on the order of the keys for the order of the array (if order matters), you'll want to change your input structure. If order doesn't matter, it is probably fine how it is.
Try this using basic for loop. Inside you will compute key dynamically and value being flattened array of Object.values of the iterating object.
var input = [{
id: 1,
food: {
fruits: ["Banana", "Orange", "Apple", "Mango"],
veggies: ["greens", "peppers", "carrot", "potatoes"]
}
},
{
id: 2,
food: {
fruits: ["grapes", "berries", "peach", "pears"],
veggies: ["cabbage", "spinach"],
dairy: ["nutmilk", "goatmilk"]
}
}
];
var temp = [];
for (var i = 0; i < input.length; i++) {
temp.push({
[`id_${input[i].id}`]: Object.values(input[i].food)
.flat(1)
.join(";")
});
}
console.log(temp); // this gives you an array
console.log(Object.assign(...temp));// in case you require one single object
I havve two different arrays with different property names like below
arrayA = [
{ id: 20, name: 'Jason' },
{ id: 15, name: 'Harry' },
{ id: 5, name: 'Clara' },
{ id: 9, name: 'Melonie' }
]
arrayB = [
{ courseID: 12, studentID: 20 },
{ courseID: 12, studentID: 15 }
]
I want to compare these two different arrays and remove unmatched ids from arrayA. For comparison, id field of arrayA and studentID field of arrayB matters. if these fileds aren't equal to each other, they should be removed from arrayA.
Expected is below
arrayA = [{id: 20, name: 'Jason' }, { id: 15, name: 'Harry' }]
Here is what I tried below but didn't work. Gave me empty array.
filteredElements = this.arrayA.map(e => e.id).filter(
val => this.arrayB.indexOf(val.studentID) !== -1
);
You can do that in following steps:
Use map() on arrayB and create array of courseID.
Then create a Set() from that Array
Then use filter() arrayA and check whether id of object exists in above created Set or not using Set.prototype.has()
const arrayA = [{id:20,name:'Jason'},{id:15,name:'Harry'},{id:5,name:'Clara'},{id:9,name:'Melonie'}]
const arrayB =[{courseID:12,studentID:20},{courseID:12,studentID:15}];
const ids = new Set(arrayB.map(x => x.studentID));
const res = arrayA.filter(x => ids.has(x.id));
console.log(res);
let arrayA = [{id: 20,name: 'Jason'},{id: 15,name: 'Harry'},{id: 5,name: 'Clara'},{id: 9,name: 'Melonie'}]
let arrayB = [{courseID: 12,studentID: 20},{courseID: 12,studentID: 15}];
let filtered=arrayA.filter(obj =>{ if(arrayB.find(course => course.studentID == obj.id))return true;return false;
});
console.log(filtered);
Try this:
var studentIds = arrayB.map(course => course.studentID);
var result = arrayA.filter(student => studentIds.includes(student.id));
The variable result contains your result.
Create a dictionary from courseMembers, keyed on studentID, to enable O(1) lookup.
Filter students according to the dictionary.
const students = [{id:20,name:'Jason'},{id:15,name:'Harry'},{id:5,name:'Clara'},{id:9,name:'Melonie'}]
const courseMembers = [{courseID:12,studentID:20},{courseID:12,studentID:15}]
function withCourses(students, courseMembers) {
const map = courseMembers.reduce((acc, {studentID}) =>
(acc[studentID] = true, acc), {})
return students.filter(({id}) => map[id])
}
const result = withCourses(students, courseMembers)
console.log(result) // [{ id:20, name:"Jason" },{ id:15, name:"Harry" }]
I have the following object:
'1': {
id: 1,
...
tags: ['cat I', 'cat II']
},
'2': {
id: 2,
tags: ['cat II', 'cat III']
}
To get all the categories ( but no duplicates ) I do the following:
const cats = [];
this.courses.forEach(data => (data.tags) ? cats.push(data.tags) : '');
return [...new Set(cats.flat())];
It works but I have the feeling this is way to "over the top". It's also runs twice because its in the computed properties.
Is there a beter way to distinct & filter out the categories. Maybe by giving a query to the store?
Use Array.flatMap() to get an array of tags. You can use destructuring and defaults to get the tags property, or assign an empty array if it's missing. To get unique tags, create a Set from the array of tags, and spread the Set back to an array:
const data = [{"id":1,"tags":["cat I","cat II"]},{"id":2,"tags":["cat II","cat III"]},{"id":3}]
const result = [...new Set(data.flatMap(({ tags = [] }) => tags))]
console.log(result)
You do:
const courses = [{id: 1, tags: ['cat I', 'cat II ']}, {id: 2, tags: ['cat II', 'cat III']}, {id: 3}]
const tags = courses
.reduce((a, { tags = [] }) => [...a, ...tags], [])
.map(tag => tag.trim()) // <-- to remove extra spaces in "cat II "
const result = [...new Set(tags)]
console.log(result)
I want to filter following two arrays and get the count of "isimplemented: 'Yes'" elements:
const arr1 = [{ProjectName: "IT", Department: "Software"}]
const arr2 = [{Name: "IT", isimplemented: "Yes"}]
I tried the following method to do the same but not getting desired result. How I can do it in JavaScript
((arr1.map(data => data.ProjectName)).filter(arr1.map(data => data.ProjectName) === arr2.map(data => data.Name) && isimplemented === "Yes")).length
You could teka a Set for the implemented projects and then count the occurences of the project who are implemented.
const
arr1 = [{ ProjectName: "IT", Department: "Software" }],
arr2 = [{ Name: "IT", isimplemented: "Yes" }],
implemented = arr2.reduce((s, { Name, isimplemented }) => isimplemented === 'Yes' ? s.add(Name) : s, new Set),
count = arr1.reduce((c, { ProjectName }) => c + implemented.has(ProjectName), 0);
console.log(count);
First merge the different arrays to create one single array
Create a variable which will keep track of your count
use forEach to iterate over the elements in the array, increment the count for every array-object having property isImplemented: 'Yes'
const arr1 = [{ProjectName: "IT", Department: "Software"}]
const arr2 = [{Name: "IT", isimplemented: "Yes"}]
const newArr = [...arr1, ...arr2]
let count = 0
newArr.forEach(element => {
if (element.isimplemented === 'Yes') {
count++
}
})
console.log(count)
I have two arrays:
The first contains unique names of fields in a nested array:
[0][0]:Name1
[0][1]:Name2
[0][2]:Name3
etc.
The second contains multiple items with values in a nested array like this:
[0][0] XYZ
[0][1] XYZA
[0][2] XYZ2
[1][0] XYZaa
[1][1] XYZas
[1][2] XYA
etc
What I want to do is to merge it and name it in this way:
[0] Name1: XYZ
[0] Name2: XYZA
[0] Name3: XYZ2
[1] Name1: XYZaa
[1] Name2: XYZas
[1] Name3: XYA
To achieve this I first attempted the following:
var mergedArr = name.concat(data);
That works fine, however I believe I can also use lodash to get closer to what I want:
_.merge(name, data)
and should work fine too.
I was trying to name it by using
_.zipObject
Yet it doesn't work the way I would like
I was trying few options with zip, zipObject, yet non of it gave me expected output.
Edit1:
how I created arrays:
$("#T1020 tr").each(function(x, z){
name[x] = [];
$(this).children('th').each(function(xx, zz){
name[x][xx] = $(this).text();
});
})
$("#T1020 tr").each(function(i, v){
data[i] = [];
$(this).children('td').each(function(ii, vv){
data[i][ii] = $(this).text();
});
})
If I understand your question correctly, you're wanting to zip array1 and array2 into a single array where:
each item of the result array is an object
the keys of each object are values of array1[0], and
the values of each key corresponding nested array of array2
To produce the following:
[
{
"name1": "xyz",
"name2": "xyza",
"name3": "xyz2"
},
{
"name1": "xyzaa",
"name2": "xyzas",
"name3": "xya"
}
]
This can be achieved without lodash; first map each item of array2 by a function where array1[0] is reduced to an object. The reduced object is composed by a key that is the current reduce item, and a value that is taken from the indexed value of the current map item:
const array1 = [
['name1', 'name2', 'name3']
]
const array2 = [
['xyz', 'xyza', 'xyz2'],
['xyzaa', 'xyzas', 'xya']
]
const result = array2.map((item) => {
/* Reduce items of array1[0] to an object
that corresponds to current item of array2 */
return array1[0].reduce((obj, value, index) => {
return { ...obj,
[value]: item[index]
};
}, {});
});
console.log(JSON.stringify(result, null, ' '));
Iterate the values (your array2) and take the sub-array from the keys (array) using the current index and the % operator. This will ensure that if that the keys are taken in a cyclic way (see example with keys2 and values2). Convert to object with _.zipObject:
const fn = (keys, values) => values.map((v, i) => _.zipObject(keys[i % keys.length], v))
const keys1 = [['name1', 'name2', 'name3']]
const values1 = [['xyz', 'xyza', 'xyz2'], ['xyzaa', 'xyzas', 'xya']]
const keys2 = [['name1', 'name2', 'name3'], ['name11', 'name12', 'name13']]
const values2 = [['xyz', 'xyza', 'xyz2'], ['xyzaa', 'xyzas', 'xya'], ['abc', 'def', 'hij']]
console.log(fn(keys1, values1))
console.log(fn(keys2, values2))
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.js"></script>