Top Collect.js Interview Questions and Answers-(2024)

1 .

Collect.js is the javascript library for collecting data from tree-based structures. This library is used on JavaScript Array and Objects. Collect.js framework that allows merchants to collect sensitive payment information from their customers without exposing their website to sensitive information.

2 .

Why Collect.js?

It is a fluent and convenient wrapper for working with arrays and objects. It provides us with different functions that help in working with data much easier. It also helps the programmers to write more concise code and easier to maintain the JavaScript code.

3 .

What is Strictness and comparisons in Collect.js?

All comparisons in collect.js are done using strict equality. Using loose equality comparisons are generally frowned upon in JavaScript. Laravel only performs "loose" comparisons by default and offer several "strict" comparison methods. These methods have not been implemented in collect.js because all methods are strict by default.

4 .

Installation in Collect.js.

Installation :

NPM

npm install collect.js --save

Yarn

yarn add collect.js

From CDN

* Visit https://cdnjs.com/libraries/collect.js

* Add CDN link to your site with <script>

Using build / minified version

* Download collect.min.js

* Add to your site with <script>

5 .

What is all() method in Collect.js?

The all method returns the underlying array or object represented by the collection :

collect([1, 2, 3]).all();

// [1, 2, 3]
collect({
  firstname: 'Darwin',
  lastname: 'Núñez',
}).all();

// {
//   firstname: 'Darwin',
//   lastname: 'Núñez',
// }

6 .

What is average() method in Collect.js?

The average() method is used to return the average of all the items in a collection. This method is an alias of avg() method.

Syntax :

collect(array).average()

Parameters : The collect() method takes one argument that is converted into the collection and then average() function is applied on it, which can take element if you apply it on the collection of objects.

Example :

const collect = require('collect.js');
  
let arr = [10, 20, 30];
  
let average = collect(arr).average();
  
console.log("Average of the given array: ", average);

Output:

Average of the given array:  20

7 .

What is avg() method in Collect.js?

The avg() method returns the average of all the items in a collection.

The collect() takes one argument that is converted into the collection and then avg() function is applied on it, which can take element if you apply it on the collection of objects.

avg() method example :

const collect = require('collect.js');
  
let arr = [
    {
      name: 'Ramana',
      score: 98,
    },
    {
      name: 'Venkat',
      score: 96,
    },
    {
        name: 'Suresh',
        score: 80
    },
  ];
  
// converting object to collection
const collection = collect(arr);
    
// finding the average of all the score
let averageScore = collection.avg('score');
    
console.log("Average score of students : ", averageScore);

Output :

Average score of students : 91.33333333333

8 .

What is the chunk() method in Collect.js?

The chunk() method breaks the collection into multiple, smaller collections of a given size :

Syntax :

data.chunk(x)

Example :

const collect = require('collect.js');
const collection = collect([1, 2, 3, 4, 5, 6, 7]);
const x = collection.chunk(5);
console.log(x.all());

Output :

 [ Collection { items: [ 1, 2, 3, 4, 5 ] },
  Collection { items: [ 6, 7 ] } ]

9 .

What are collapse() and combine() methods in Collect.js?

collapse() : The collapse() method collapses a collection of arrays into a single, flat collection :

const collection = collect([[1], [{}, 5, {}], ['xoxo']]);

const collapsed = collection.collapse();

collapsed.all();

// [1, {}, 5, {}, 'xoxo']

const collection = collect([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);

const collapsed = collection.collapse();

collapsed.all();

// [1, 2, 3, 4, 5, 6, 7, 8, 9]

combine() : The combine() method combines the keys of the collection with the values of another array or collection :

const collection = collect(['name', 'number']);

const combine = collection.combine(['Free Time Learn', 12]);

combine.all();

// {
//   name: 'Free Time Learn',
//   number: 12
// }

10 .

What is concat() method in Collect.js?

concat() : The concat() method is used to merge two or more collections/arrays/objects :

You can also concat() an array of objects, or a multidimensional array

const collection = collect([1, 2, 3]);

let concatenated = collection.concat(['a', 'b', 'c']);

concatenated = concatenated.concat({
  name: 'Free Time Learning',
  number: 12,
});

concatenated.all();

// [1, 2, 3, 'a', 'b', 'c', 'Free Time Learn', 12]

11 .

What is contains() method in Collect.js?

contains() : The contains() method determines whether the collection contains a given item :

const collection = collect({
  name: 'Free Time Learn',
  number: 12,
});

collection.contains('name');
// true

collection.contains('age');
// false

collection.contains('Free Time Learn');
// true

You may also work with arrays

const collection = collect([1, 2, 3]);

collection.contains(3);
// true

You may also pass a key / value pair to the contains method, which will determine if the given pair exists in the collection:

const collection = collect({
  name: 'Free Time Learn',
  number: 12,
});

collection.contains('name', 'Steve Jobs');
// false

Finally, you may also pass a callback to the contains method to perform your own truth test:

const collection = collect([1, 2, 3, 4, 5]);

collection.contains((value, key) => value > 5);

// false

12 .

Explain containsOneItem() method in Collect.js?

containsOneItem() : The containsOneItem() method returns true if the collection contains exactly one item; otherwise, false is returned.

collect([1]).containsOneItem();
// true

collect({ firstname: 'Luis' }).containsOneItem();
// true

collect('value').containsOneItem();
// true

collect([1, 2, 3]).containsOneItem();
//  false

collect({ firstname: 'Luis', lastname: 'Díaz' }).containsOneItem();
// false

collect().containsOneItem();
// false

collect([]).containsOneItem();
// false

collect({}).containsOneItem();
// false

13 .

What is count() and countBy() methods in Collect.js?

count() : The count() method returns the total number of items in the collection.

const collection = collect([1, 2, 3, 4]);

collection.count();

// 4

countBy() : The countBy() method counts the occurences of values in the collection. By default, the method counts the occurrences of every element:

const collection = collect([1, 2, 2, 2, 3]);

const counted = collection.countBy();

counted.all();

// {
//   1: 1,
//   2: 3,
//   3: 1,
// }

However, you pass a callback to the countBy() method to count all items by a custom value:

const collection = collect([
  'freetimelearn@gmail.com',
  'info@freetimelearning.com',
  'vvramanareddy9963@gmail.com',
]);

const counted = collection.countBy(email => email.split('@')[1]);

counted.all();

// {
//   'gmail.com': 2,
//   'freetimelearning.com': 1,
// }

14 .

What is the crossJoin() method in Collect.js?

crossJoin() : The crossJoin() method cross joins the collection with the given array or collection, returning all possible permutations:

const collection = collect([1, 2]);

const joined = collection.crossJoin(['a', 'b']);

joined.all();

// [
//   [1, 'a'],
//   [1, 'b'],
//   [2, 'a'],
//   [2, 'b'],
// ]

15 .

What is dd() and diff() methods in Collect.js?

dd() : The dd() method will console.log the collection and exit the current process:

const collection = collect([1, 2, 3]).dd();

// Collection { items: [ 1, 2, 3 ] }
// (Exits node.js process)

diff() : The diff() method compares the collection against another collection or a plain array based on its values. This method will return the values in the original collection that are not present in the given collection:

const collection = collect([1, 2, 3, 4, 5]);

const diff = collection.diff([1, 2, 3, 9]);

diff.all();

// [4, 5]

16 .

What is diffAssoc() and diffKeys() methods in Collect.js?

diffAssoc() : The diffAssoc() method compares the collection against another collection or a plain object based on its keys and values. This method will return the key / value pairs in the original collection that are not present in the given collection:

const collection = collect({
  color: 'orange',
  type: 'fruit',
  remain: 6,
});

const diff = collection.diffAssoc({
  color: 'yellow',
  type: 'fruit',
  remain: 3,
  used: 6,
});

diff.all();

// { color: 'orange', remain: 6 };

diffKeys() : The diffKeys() method compares the collection against another collection or a plain object based on its keys. This method will return the key / value pairs in the original collection that are not present in the given collection:

const collection = collect({
  a: 'a',
  b: 'b',
  c: 'c',
  d: 'd',
});

const diff = collection.diffKeys({
  b: 'b',
  d: 'd',
});

diff.all();

// { a: 'a', c: 'c' }

17 .

What is doesntContain() method in Collect.js?

doesntContain() : The doesntContain() method determines whether the collection does not contain a given item. You may pass a closure to the doesntContain method to determine if an element does not exist in the collection matching a given truth test:

const collection = collect([1, 2, 3, 4, 5]);

collection.doesntContain(value => value < 5);

// false

const collection = collect([1, 2, 3]);

collection.doesntContain(4);
// true

You may also use doesntContain on object based collections:

const collection = collect({
  name: 'Free Time Learn',
  number: 12,
});

collection.doesntContain('Free Time Learn');
// false

collection.doesntContain('Darwin Núñez');
// true

You may also pass a key / value pair to the contains method, which will determine if the given pair exists in the collection:

const collection = collect({
  name: 'Free Time Learn',
  number: 11,
});

collection.doesntContain('name', 'Darwin Núñez');
// true

18 .

What is dump() and duplicates() methods in Collect.js?

dump() : The dump() method outputs the results at that moment and then continues processing:

collect([1, 2, 3, 4])
  .dump()
  .map(item => item * 2)
  .dump();

// Collection { items: [ 1, 2, 3, 4 ] }
// Collection { items: [ 2, 4, 6, 8 ] }

duplicates() : The duplicates() method retrieves and returns duplicate values from the collection:

const collection = collect(['a', 'b', 'a', 'c', 'b']);

const duplicates = collection.duplicates();

duplicates.all();

// { 2: 'a', 4: 'b' }

19 .

What is each() and eachSpread() methods in Collect.js?

each() : The each() method iterates over the items in the collection and passes each item to a callback:

let sum = 0;

const collection = collect([1, 3, 3, 7]);

collection.each((item) => {
  sum += item;
});

// console.log(sum);
// 14

If you would like to stop iterating through the items, you may return false from your callback:

let sum = 0;

const collection = collect([1, 3, 3, 7]);

collection.each((item) => {
  sum += item;

  if (sum > 5) {
    return false;
  }
});

// console.log(sum);
// 7

eachSpread() : The eachSpread() method iterates over the collection's items, passing each nested item value into the given callback:

const collection = collect([['John Doe', 35], ['Jane Doe', 33]]);

collection.eachSpread((name, age) => {
  //
});

You may stop iterating through the items by returning false from the callback:

collection.eachSpread((name, age) => false);

20 .

What is the every() and except() methods in Collect.js?

every() : The every() method may be used to verify that all elements of a collection pass a given truth test:

collect([1, 2, 3, 4]).every((value, key) => value > 2);

// false

except() : The except() method returns all items in the collection except for those with the specified keys:

const collection = collect({
  product_id: 1,
  price: 100,
  discount: false,
});

const filtered = collection.except(['price', 'discount']);

filtered.all();

// { product_id: 1 }

collect([1, 2, 3, 4])
  .except([2, 12])
  .all();

// [1, 3, 4]

For the inverse of except, see the only method.

21 .

What about filter() and reject() methods in Collect.js?

filter() : The filter() method filters the collection using the given callback, keeping only those items that pass a given truth test:

const collection = collect([1, 2, 3, 4]);

const filtered = collection.filter((value, key) => value > 2);

filtered.all();

// [3, 4]

If no callback is supplied, all entries of the collection that are equivalent to false will be removed :

const collection = collect([
  0,
  1,
  2,
  null,
  3,
  4,
  undefined,
  5,
  6,
  7,
  [],
  8,
  9,
  {},
  10,
]);

const filtered = collection.filter();

filtered.all();

// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

For the inverse of filter, see the reject method.

reject() : The reject() method filters the collection using the given callback. The callback should return true if the item should be removed from the resulting collection:

const collection = collect([1, 2, 3, 4]);

const filtered = collection.reject(value => value > 2);

// [1, 2]

For the inverse of the reject method, see the filter method.

22 .

What about first(), firstOrFail() and firstWhere() methods in Collect.js?

first() : The first() method returns the first element in the collection that passes a given truth test:

collect([1, 2, 3, 4]).first(item => item > 1);

// 2

You may also call the first method with no arguments to get the first element in the collection. If the collection is empty, null is returned:

collect([1, 2, 3, 4]).first();

// 1

firstOrFail() : The firstOrFail() method returns the first element in the collection, or throws an error if there are no elements:

collect([1, 2, 3, 4]).firstOrFail(item => item > 1);

// 2
collect([1, 2, 3, 4]).firstOrFail(item => item > 4);

// Error ('Item not found.') is thrown.

You may also call the firstOrFail method with no arguments to get the first element in the collection. If the collection is empty, an error is thrown:

collect([1, 2, 3, 4]).firstOrFail();

// 1
collect().firstOrFail();

// Error ('Item not found.') is thrown.

Like the where method, you may also pass an attribute, operator, and value:

const collection = collect([
  { product: 'Desk', price: 200, discounted: true },
  { product: 'Chair', price: 100, discounted: true },
  { product: 'Bookcase', price: 150, discounted: true },
  { product: 'Door', price: 100 },
]);

collection.firstOrFail('product', '=', 'Desk');

// { product: 'Desk', price: 200, discounted: true }

firstWhere() : The firstWhere() method returns the first element in the collection with the given key / value pair:

const collection = collect([
  { name: 'Regena', age: 12 },
  { name: 'Linda', age: 14 },
  { name: 'Diego', age: 23 },
  { name: 'Linda', age: 84 },
]);

collection.firstWhere('name', 'Linda');

// { name: 'Linda', age: 14 }

23 .

What is the flatMap() method in Collect.js?

flatMap() : The flatMap() method iterates through the collection and passes each value to the given callback. The callback is free to modify the item and return it, thus forming a new collection of modified items. Then, the array is flattened by a level:

const collection = collect([
  {
    name: 'Ramana Reddy',
    number: 27,
  },
  {
    name: 'Free Time Learn',
    number: 11,
  },
]);

const flatMapped = collection.flatMap(value => value.name.toUpperCase());

flatMapped.all();

// ['RAMANA REDDY', 'FREE TIME LEARN']

24 .

What about flatten() method in Collect.js?

flatten() : The flatten() method flattens a multi-dimensional collection into a single dimension:

const collection = collect({
  club: 'Liverpool',
  players: ['Salah', 'Firmino', 'Núñez'],
});

const flattened = collection.flatten();

flattened.all();

// ['Liverpool', 'Salah', 'Firmino', 'Núñez'];

You may optionally pass the function a "depth" argument:

const collection = collect({
  Apple: [
    {
      name: 'iPhone 6S',
      brand: 'Apple',
    },
  ],
  Samsung: [
    {
      name: 'Galaxy S7',
      brand: 'Samsung',
    },
  ],
});

const flattened = collection.flatten(1);

flattened.all();

// [
//   { name: 'iPhone 6S', brand: 'Apple' },
//   { name: 'Galaxy S7', brand: 'Samsung' },
// ]

In this example, calling flatten without providing the depth would have also flattened the nested arrays, resulting in ['iPhone 6S', 'Apple', 'Galaxy S7', 'Samsung']. Providing a depth allows you to restrict the levels of nested arrays that will be flattened.

25 .

What is flip() method in Collect.js?

flip() : The flip() method swaps the collection's keys with their corresponding values:

const collection = collect({
  name: 'Free Time Learn',
  number: 31,
});

const flipped = collection.flip();

flipped.all();

// {
//   'Free Time Learn': 'name',
//   '31': 'number',
// }

26 .

What about forPage(), get() and forget() methods in Collect.js?

forPage() : The forPage() method returns a new collection containing the items that would be present on a given page number. The method accepts the page number as its first argument and the number of items to show per page as its second argument:

const collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9]);

const forPage = collection.forPage(2, 3);

forPage.all();

// [4, 5, 6]

get() : The get() method returns the item at a given key or index. If the key or index does not exist, null is returned:

const collection = collect({
  firstname: 'Mohamed',
  lastname: 'Salah',
});

collection.get('lastname');

// Salah

collection.get('middlename');

// null
const collection = collect(['a', 'b', 'c']);

collection.get(1);

// b

You may optionally pass a default value as the second argument:

const collection = collect({
  firstname: 'Mohamed',
  lastname: 'Salah',
});

collection.get('middlename', 'default-value');
// default-value

You may even pass a callback as the default value. The result of the callback will be returned if the specified key does not exist:

const collection = collect({
  firstname: 'Mohamed',
  lastname: 'Salah',
});

collection.get('middlename', () => 'default-value');

// default-value

forget() : The forget() method removes an item from the collection by its key:

const collection = collect({
  name: 'Darwin Núñez',
  number: 27,
});

collection.forget('number');

collection.all();

// {
//   name: 'Darwin Núñez',
// }

Unlike most other collection methods, forget does not return a new modified collection; it modifies the collection it is called on.

27 .

What is groupBy() method in Collect.js?

groupBy() : The groupBy() method groups the collection's items into multiple collections by a given key:

If you want to group the collection by keys as a plain object, see mapToGroups

const collection = collect([
  {
    product: 'Chair',
    manufacturer: 'IKEA',
  },
  {
    product: 'Desk',
    manufacturer: 'IKEA',
  },
  {
    product: 'Chair',
    manufacturer: 'Herman Miller',
  },
]);

const grouped = collection.groupBy('manufacturer');

grouped.all();

// {
//   IKEA: Collection {
//     items: [
//        {
//          id: 100,
//          product: 'Chair',
//          manufacturer: 'IKEA',
//          price: '1490 NOK',
//        },
//        {
//          id: 150,
//          product: 'Desk',
//          manufacturer: 'IKEA',
//          price: '900 NOK',
//        },
//      ],
//   },
//   'Herman Miller': Collection {
//     items: [
//       {
//         id: 200,
//         product: 'Chair',
//         manufacturer: 'Herman Miller',
//         price: '9990 NOK',
//       },
//     ],
//   },
// }

In addition to passing a string key, you may also pass a callback. The callback should return the value you wish to key the group by:

const collection = collect([
  {
    product: 'Chair',
    manufacturer: 'IKEA',
  },
  {
    product: 'Desk',
    manufacturer: 'IKEA',
  },
  {
    product: 'Chair',
    manufacturer: 'Herman Miller',
  },
]);

const grouped = collection.groupBy((item, key) => item.manufacturer.substring(0, 3));

grouped.all();

// {
//   IKE: Collection {
//     items: [
//       {
//         id: 100,
//         product: 'Chair',
//         manufacturer: 'IKEA',
//         price: '1490 NOK',
//       },
//       {
//         id: 150,
//         product: 'Desk',
//         manufacturer: 'IKEA',
//         price: '900 NOK',
//       },
//     ],
//   },
//   Her: Collection {
//     items: [
//       {
//         id: 200,
//         product: 'Chair',
//         manufacturer: 'Herman Miller',
//         price: '9990 NOK',
//       },
//     ],
//   },
// }

28 .

What is implode() method in Collect.js?

implode() : The implode() method joins the items in a collection. Its arguments depend on the type of items in the collection. If the collection contains arrays or objects, you should pass the key of the attributes you wish to join, and the "glue" string you wish to place between the values:

const collection = collect([
  {
    product: 'Chair',
    manufacturer: 'IKEA',
  },
  {
    product: 'Desk',
    manufacturer: 'IKEA',
  },
  {
    product: 'Chair',
    manufacturer: 'Herman Miller',
  },
]);

collection.implode('product', ',');

// Chair, Desk, Chair

If the collection contains simple strings or numeric values, simply pass the "glue" as the only argument to the method:

collect([1, 2, 3, 4, 5]).implode('-');

// 1-2-3-4-5

29 .

What about intersect() and intersectByKeys() methods in Collect.js?

intersect() : The intersect() method removes any values from the original collection that are not present in the given array or collection. The resulting collection will preserve the original collection's keys:

const collection = collect([1, 2, 3, 4, 5]);

intersect = collection.intersect([1, 2, 3, 9]);

intersect.all();

// [1, 2, 3]

intersectByKeys() : The intersectByKeys() method removes any keys from the original collection that are not present in the given array or collection:

const collection = collect({
  serial: 'UX301',
  type: 'screen',
  year: 2009,
});

const intersect = collection.intersectByKeys({
  reference: 'UX404',
  type: 'tab',
  year: 2011,
});

intersect.all();

// { type: 'screen', year: 2009 }

const firstCollection = collect([1, 2, 3, 4, 5]);
const secondCollection = collect([1, 2, 3, 9]);

intersect = firstCollection.intersect(secondCollection);

intersect.all();

// [1, 2, 3]

30 .

What is the isEmpty() and isNotEmpty() methods in Collect.js?

isEmpty() : The isEmpty method returns true if the collection is empty; otherwise, false is returned:

collect().isEmpty();
// true

collect([]).isEmpty();
// true

collect({}).isEmpty();
// true

isNotEmpty() : The isNotEmpty() method returns true if the collection is not empty; otherwise, false is returned:

collect([1, 2, 3]).isNotEmpty();
//  true

collect().isNotEmpty();
// false

collect([]).isNotEmpty();
// false

collect({}).isNotEmpty();
// false

31 .

What is join() method in Collect.js?

join() : The join() method joins the collection's values with a string:

collect(['a', 'b', 'c']).join(', ');
// 'a, b, c'

collect(['a', 'b', 'c']).join(', ', ', and ');
// 'a, b, and c'

collect(['a', 'b']).join(', ', ' and ');
// 'a and b'

collect(['a']).join(', ', ' and ');
// 'a'

collect([]).join(', ', ' and ');
// ''

32 .

What is the keyBy() and keys() method in Collect.js?

keyBy() : The keyBy() method keys the collection by the given key. If multiple items have the same key, only the last one will appear in the new collection:

const collection = collect([
  {
    product: 'Chair',
    manufacturer: 'IKEA',
  },
  {
    product: 'Desk',
    manufacturer: 'IKEA',
  },
  {
    product: 'Chair',
    manufacturer: 'Herman Miller',
  },
]);

const keyed = collection.keyBy('manufacturer');

keyed.all();

// {
//   IKEA: {
//     product: 'Desk',
//     manufacturer: 'IKEA',
//   },
//   'Herman Miller': {
//     product: 'Chair',
//     manufacturer: 'Herman Miller',
//   },
// }

You may also pass a callback to the method. The callback should return the value to key the collection by:

const upperCased = collection.keyBy(item => item.manufacturer.toUpperCase());

upperCased.all();

// {
//   IKEA: {
//     product: 'Desk',
//     manufacturer: 'IKEA',
//   },
//   'HERMAN MILLER': {
//     product: 'Chair',
//     manufacturer: 'Herman Miller',
//   },
// }

keys() : The keys() method returns all of the collection's keys:

const collection = collect([
  {
    club: 'Liverpool',
    nickname: 'The Reds',
  },
]);

keys = collection.keys();

// ['club', 'nickname']

33 .

What about last(), macro() and make() methods in Collect.js?

last() : The last() method returns the last element in the collection that passes a given truth test:

const collection = collect([1, 2, 3]);

const last = collection.last(item => item > 1);

// 3

You may also call the last method with no arguments to get the last element in the collection. If the collection is empty, null is returned:

collect([1, 2, 3, 4]).last();

// 4

macro() : The macro() method lets you register custom methods

collect().macro('uppercase', function () {
  return this.map(item => item.toUpperCase());
});

const collection = collect(['a', 'b', 'c']);

collection.uppercase();

collection.all();

// ['A', 'B', 'C']

Note that the macro method returns undefined, and therefore it is not possible to use it within a chain of methods.

make() : The make() method creates a new collection instance.

This is only added to adhere to the Laravel collection API, when using Collect.js it's recommended to use collect() directly when creating a new collection.

34 .

Explain map methods in Collect.js.

map() : The map() method iterates through the collection and passes each value to the given callback. The callback is free to modify the item and return it, thus forming a new collection of modified items:

const collection = collect([1, 2, 3, 4, 5]);

const multiplied = collection.map(item => item * 2);

multiplied.all();

// [2, 4, 6, 8, 10]

Like most other collection methods, map returns a new collection instance; it does not modify the collection it is called on. If you want to transform the original collection, use the transform method.

mapInto() : The mapInto() method iterates through the collection and instantiates the given class with each element as a constructor:

const Player = function (name) {
  this.name = name;
};

const collection = collect([
  'Roberto Firmino',
  'Darwin Núñez',
]);

const players = collection.mapInto(Player);

players.all();

// [
//   Player { name: 'Roberto Firmino' },
//   Player { name: 'Darwin Núñez' },
// ]

mapSpread() : The mapSpread() method iterates over the collection's items, passing each nested item value into the given callback. The callback is free to modify the item and return it, thus forming a new collection of modified items:

const collection = collect([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);

const chunks = collection.chunk(2);

const sequence = chunks.mapSpread((even, odd) => even + odd);

sequence.all();

// [1, 5, 9, 13, 17]

mapToDictionary() : Run a dictionary map over the items. The callback should return an associative array with a single key/value pair.

const collection = collect([
  { id: 1, name: 'a' },
  { id: 2, name: 'b' },
  { id: 3, name: 'c' },
  { id: 4, name: 'b' },
]);

const groups = collection.mapToDictionary(item => [item.name, item.id]);

groups.all();

// {
//   a: [1],
//   b: [2, 4],
//   c: [3],
// }

mapToGroups() : The mapToGroups() method iterates through the collection and passes each value to the given callback:

const collection = collect([
  { id: 1, name: 'A' },
  { id: 2, name: 'B' },
  { id: 3, name: 'C' },
  { id: 4, name: 'B' },
]);

const groups = collection.mapToGroups((item, key) => [item.name, item.id]);

// {
//   A: [1],
//   B: [2, 4],
//   C: [3],
// }

mapWithKeys() : The mapWithKeys() method iterates through the collection and passes each value to the given callback. The callback should return an array where the first element represents the key and the second element represents the value pair:

const collection = collect([
  {
    name: 'John',
    department: 'Sales',
    email: 'john@example.com',
  },
  {
    name: 'Jane',
    department: 'Marketing',
    email: 'jane@example.com',
  },
]);

const keyed = collection.mapWithKeys(item => [item.email, item.name]);

keyed.all();

// {
//   'john@example.com': 'John',
//   'jane@example.com': 'Jane',
// }

35 .

What is max() method in Collect.js?

max() : The max() method returns the maximum value of a given key:

const collection = collect([
  {
    value: 10,
  },
  {
    value: -13,
  },
  {
    value: 12,
  },
  {
    unicorn: false,
  },
]);

const max = collection.max('value');

// 12
collect([-1, -2345, 12, 11, 3]).max();

// 12

36 .

Explain merge methods in Collect.js

merge() : The merge() method merges the given object into the original collection. If a key in the given object matches a key in the original collection, the given objects value will overwrite the value in the original collection:

const collection = collect({
  id: 1,
  price: 29,
});

const merged = collection.merge({
  price: 400,
  discount: false,
});

merged.all();

// { id: 1, price: 400, discount: false }

If our collection is an array, the values will be appended to the end of the collection:

const collection = collect(['Unicorn', 'Rainbow']);

const merged = collection.merge(['Sunshine', 'Rainbow']);

merged.all();

// ['Unicorn', 'Rainbow', 'Sunshine', 'Rainbow']

mergeRecursive() : The mergeRecursive() method merges the given array or collection recursively with the original collection. If a string key in the given items matches a string key in the original collection, then the values for these keys are merged together into an array, and this is done recursively:

const collection = collect({
  product_id: 1,
  price: 100,
});

const merged = collection.mergeRecursive({
  product_id: 2,
  price: 200,
  discount: false,
});

merged.all();

// {
//   product_id: [1, 2],
//   price: [100, 200],
//   discount: false,
// }

37 .

What is min() method in Collect.js?

min() : The min() method returns the minimum value of a given key:

const collection = collect([
  {
    worth: 100,
  },
  {
    worth: 900,
  },
  {
    worth: 79,
  },
]);

collection.min('worth');

// 79
collect([1, 2, 3, 4, 5]).min();

// 1

38 .

What is pad() and partition() methods in Collect.js?

pad() : The pad() method will fill the array with the given value until the array reaches the specified size. This method behaves like the array_pad PHP function.

To pad to the left, you should specify a negative size. No padding will take place if the absolute value of the given size is less than or equal to the length of the array:

const collection = collect(['A', 'B', 'C']);

let filtered = collection.pad(5, 0);

filtered.all();

// ['A', 'B', 'C', 0, 0]

filtered = collection.pad(-5, 0);

filtered.all();

// [0, 0, 'A', 'B', 'C']

partition() : The partition() method may be combined with destructuring to separate elements that pass a given truth test from those that do not:

const collection = collect([1, 2, 3, 4, 5, 6]);

const [underThree, overThree] = collection.partition(i => i < 3);

39 .

Explain pull(), push() and put() method in Collect.js

pull() : The pull() method removes and returns an item from the collection by its key:

const collection = collect({
  firstname: 'Michael',
  lastname: 'Cera',
});

collection.pull('lastname');

// Cera

collection.all();

// { firstname: 'Michael' }

push() : The push() method appends an item to the end of the collection:

const collection = collect([1, 2, 3, 4]);

collection.push(5);

collection.all();

// [1, 2, 3, 4, 5]

put() : The put() method sets the given key and value in the collection:

const collection = collect(['JavaScript', 'Python']);

collection.put('Ruby');

collection.all();

// ['JavaScript', 'Python', 'Ruby']

40 .

What is random() and reduce() methods in Collect.js?

random() : The random() method returns a random item from the collection:

const collection = collect([1, 2, 3, 4, 5]);

collection.random();

// 4 (retrieved randomly)

You may optionally pass an integer to random to specify how many items you would like to randomly retrieve. A collection of items is always returned when explicitly passing the number of items you wish to receive:

const threeRandom = collection.random(3);

// Collection { items: [ 5, 3, 4 ] } (retrieved randomly)

const oneRandom = collection.random(1);

// Collection { items: [ 3 ] } (retrieved randomly)

oneRandom.all();

// [3]

reduce() : The reduce() method reduces the collection to a single value, passing the result of each iteration into the subsequent iteration:

const collection = collect([1, 2, 3]);

const total = collection.reduce((carry, item) => carry + item);

// 6
The value for carry on the first iteration is null; however, you may specify its initial value by passing a second argument to reduce:

const total = collection.reduce((carry, item) => carry + item, 4);

// 10

41 .

What is replace() and replaceRecursive() methods in Collect.js?

replace() : The replace() method behaves similarly to merge; however, in addition to overwriting matching items with string keys, the replace method will also overwrite items in the collection that have matching numeric keys:

const collection = collect({
  name: 'Bob',
});

const replaced = collection.replace({
  name: 'John',
  number: 45,
});

replaced.all();

// {
//   name: 'John',
//   number: 45,
// }

replaceRecursive() : This method works like replace, but it will recurse into arrays and apply the same replacement process to the inner values:

const collection = collect([
  'Matip',
  'van Dijk',
  [
    'Núñez',
    'Firmino',
    'Salah',
  ],
]);

const replaced = collection.replaceRecursive({
  0: 'Gomez',
  2: { 1: 'Origi' },
});

replaced.all();

// {
//   0: 'Gomez',
//   1: 'van Dijk',
//   2: { 0: 'Núñez', 1: 'Origi', 2: 'Salah' },
// }

42 .

What is search() method in Collect.js?

search() : The search() method searches the collection for the given value and returns its key if found. If the item is not found, false is returned.

const collection = collect([2, 4, 6, 8]);

collection.search(4);

// 1

The search is done using a "loose" comparison, meaning a string with an integer value will be considered equal to an integer of the same value. To use strict comparison, pass true as the second argument to the method :

collection.search('4', true);

// false
Alternatively, you may pass in your own callback to search for the first item that passes your truth test:

collection.search((item, key) => item > 5);

// 2

43 .

What is shift() method in Collect.js?

shift() : The shift() method removes and returns the first item from the collection :

const collection = collect([1, 2, 3, 4, 5]);

collection.shift();

// 1

collection.all();

// [2, 3, 4, 5]

You may provide number of items to shift. This will return the shifted items in a new collection :

const collection = collect([1, 2, 3, 4, 5]);

collection.shift(2).all();

// [1, 2]

collection.all();

// => [3, 4, 5]

44 .

What about shuffle() and skip() methods in Collect.js?

shuffle() : The shuffle() method randomly shuffles the items in the collection:

const collection = collect([1, 2, 3, 4, 5]);

const shuffled = collection.shuffle();

shuffled.all();

// [3, 5, 1, 2, 4] (generated randomly)

skip() : The skip() method returns a new collection, without the first given amount of items:

const collection = collect([1, 2, 3, 4, 5, 6]);

collection.skip(4).all();

// [5, 6]
const collection = collect({
  first: 'first',
  second: 'second',
  third: 'third',
  fourth: 'fourth',
  fifth: 'fifth',
});

collection.skip(4).all();

// { fifth: 'fifth' }

45 .

What is skipUntill() and skipWhile() methods in Collect.js?

skipUntil() : The skipUntil() method skips items until the given callback returns true and then returns the remaining items in the collection:

const collection = collect([1, 2, 3, 4]);

const subset = collection.skipUntil(item => item >= 3);

subset.all();

// [3, 4]

You may also pass a simple value to the skipUntil method to skip all items until the given value is found:

const collection = collect([1, 2, 3, 4]);

const subset = collection.skipUntil(3);

subset.all();

// [3, 4]

skipWhile() : The skipWhile() method skips items while the given callback returns true and then returns the remaining items in the collection:

const collection = collect([1, 2, 3, 4]);

const subset = collection.skipWhile(item => item <= 3);

subset.all();

// [4]

If the callback never returns true, the skipWhile() method will return an empty collection.

You may also pass a simple value to the skipWhile:

const collection = collect([1, 1, 2, 2, 3, 3, 4, 4]);

const subset = collection.skipWhile(1);

subset.all();

// [2, 2, 3, 3, 4, 4]

46 .

Explain sort methods in Collect.js.

sort() : The sort() method sorts the collection:

const collection = collect([5, 3, 1, 2, 4]);

const sorted = collection.sort();

sorted.all();

// [1, 2, 3, 4, 5]

If your sorting needs are more advanced, you may pass a callback to sort with your own algorithm.

const collection = collect([5, 3, 1, 2, 4]);

const sorted = collection.sort((a, b) => b - a);

sorted.all();

// [5, 4, 3, 2, 1]

If you need to sort a collection of nested arrays or objects, see the sortBy and sortByDesc methods.

sortBy() : The sortBy() method sorts the collection by the given key. The sorted collection keeps the original array keys, so in this example we'll use the values method to reset the keys to consecutively numbered indexes:

const collection = collect([
  { name: 'Desk', price: 200 },
  { name: 'Chair', price: 100 },
  { name: 'Bookcase', price: 150 },
]);

const sorted = collection.sortBy('price');

sorted.all();

// [
//   { name: 'Chair', price: 100 },
//   { name: 'Bookcase', price: 150 },
//   { name: 'Desk', price: 200 },
// ]

You can use dot notation to sort by nested values

const collection = collect([
  {
    name: 'Desk',
    price: 200,
    manufacturer: {
      name: 'IKEA',
    },
  },
  {
    name: 'Chair',
    price: 100,
    manufacturer: {
      name: 'Herman Miller',
    },
  },
  {
    name: 'Bookcase',
    price: 150,
    manufacturer: {
      name: 'IKEA',
    },
  },
]);

const sorted = collection.sortBy('manufacturer.name');

sorted.all();

// [
//   {
//     name: 'Chair',
//     price: 100,
//     manufacturer: {
//       name: 'Herman Miller',
//     },
//   },
//   {
//     name: 'Desk',
//     price: 200,
//     manufacturer: {
//       name: 'IKEA',
//     },
//   },
//   {
//     name: 'Bookcase',
//     price: 150,
//     manufacturer: {
//       name: 'IKEA',
//     },
//   },
// ]

You can also pass your own callback to determine how to sort the collection values:

const collection = collect([
  { name: 'Desk', colors: ['Black', 'Mahogany'] },
  { name: 'Chair', colors: ['Black'] },
  { name: 'Bookcase', colors: ['Red', 'Beige', 'Brown'] },
]);

const sorted = collection.sortBy((product, key) => product.colors.length);

sorted.all();

// [
//   { name: 'Chair', colors: ['Black'] },
//   { name: 'Desk', colors: ['Black', 'Mahogany'] },
//   { name: 'Bookcase', colors: ['Red', 'Beige', 'Brown'] },
// ]

sortByDesc() : This method has the same signature as the sortBy method, but will sort the collection in the opposite order.

sortDesc() : This method will sort the collection in the opposite order as the sort method.

const collection = collect([1, 3, 5, 2, 4]);

const sorted = collection.sortDesc();

sorted.all();

// [5, 4, 3, 2, 1]

Unlike sort, you may not pass a callback to sortDesc. If you wish to use a callback, you should use sort and invert your comparison.

sortKeys() : The sortKeys() method sorts the collection by the keys of the underlying associative array:

const collection = collect({
  id: 10,
  first: 'Darwin',
  last: 'Núñez',
});

const sorted = collection.sortKeys();

sorted.all();

// {
//   first: 'Darwin',
//   id: 10,
//   last: 'Núñez',
// }

sortKeysDesc() : This method has the same signature as the sortKeys method, but will sort the collection in the opposite order.

47 .

What is sum() method in Collect.js?

sum() : The sum() method returns the sum of all items in the collection :

collect([1, 2, 3]).sum();

// 6

If the collection contains nested arrays or objects, you should pass a key to use for determining which values to sum :

const collection = collect([
  { name: 'My story', pages: 176 },
  { name: 'Fantastic Beasts and Where to Find Them', pages: 1096 },
]);

collection.sum('pages');

// 1272

In addition, you may pass your own callback to determine which values of the collection to sum :

const collection = collect([
  { name: 'Desk', colors: ['Black', 'Mahogany'] },
  { name: 'Chair', colors: ['Black'] },
  { name: 'Bookcase', colors: ['Red', 'Beige', 'Brown'] },
]);

const total = collection.sum(product => product.colors.length);

// 6

48 .

Explain take(), takeUntil() and takeWhile() methods in Collect.js?

take() : The take() method returns a new collection with the specified number of items: You may also pass a negative integer to take the specified amount of items from the end of the collection:

const collection = collect([0, 1, 2, 3, 4, 5]);

const chunk = collection.take(3);

chunk.all();

// [0, 1, 2]

takeUntil() : The takeUntil() method returns items in the collection until the given callback returns true:

const collection = collect([1, 2, 3, 4]);

const subset = collection.takeUntil(item => item >= 3);

subset.all();

// [1, 2]

If the given value is not found or the callback never returns true, the takeUntil method will return all items in the collection.

You may also pass a simple value to the takeUntil() method to get the items until the given value is found:

const collection = collect([1, 2, 3, 4]);

const subset = collection.takeUntil(3);

subset.all();

// [1, 2]

takeWhile() : The takeWhile() method returns items in the collection until the given callback returns false:

const collection = collect([1, 2, 3, 4]);

const subset = collection.takeWhile(item => item < 3);

subset.all();

// [1, 2]

If the callback never returns false, the takeWhile method will return all items in the collection.

49 .

What is times() method in Collect.js?

times() : The times() method creates a new collection by invoking the callback a given amount of times:

const collection = collect().times(10, number => number * 9);

collection.all();

// [9, 18, 27, 36, 45, 54, 63, 72, 81, 90]

50 .

What is the toArray() and toJson() methods in Collect.js?

toArray() : The toArray() method converts the collection into a plain array. If the collection is an object, an array containing the values will be returned.

const collection = collect([1, 2, 3, 'b', 'c']);

collection.toArray();

// [1, 2, 3, 'b', 'c']
const collection = collect({
  name: 'Elon Musk',
  companies: ['Tesla', 'Space X', 'SolarCity'],
});

collection.toArray();

// ['Elon Musk', ['Tesla', 'Space X', 'SolarCity']]â€‹

toJson() : The toJson() method converts the collection into JSON string:

const collection = collect({
  id: 384,
  name: 'Rayquaza',
  gender: 'NA',
});

const json = collection.toJson();

// {"id": 384, "name": "Rayquaza", "gender": "NA"}

51 .

What is the unique() method in Collect.js?

unique() : The unique() method returns all of the unique items in the collection:

const collection = collect([1, 1, 1, 2, 3, 3]);

const unique = collection.unique();

unique.all();

// [1, 2, 3]

When dealing with an array of objects, you may specify the key used to determine uniqueness:

const collection = collect([
  { name: 'iPhone 6', brand: 'Apple', type: 'phone' },
  { name: 'iPhone 5', brand: 'Apple', type: 'phone' },
  { name: 'Apple Watch', brand: 'Apple', type: 'watch' },
  { name: 'Galaxy S6', brand: 'Samsung', type: 'phone' },
  { name: 'Galaxy Gear', brand: 'Samsung', type: 'watch' },
]);

const unique = collection.unique('brand');

unique.all();

// [
//   { name: 'iPhone 6', brand: 'Apple', type: 'phone' },
//   { name: 'Galaxy S6', brand: 'Samsung', type: 'phone' },
// ]

You may also pass your own callback to determine item uniqueness :

const collection = collect([
  { name: 'iPhone 6', brand: 'Apple', type: 'phone' },
  { name: 'iPhone 5', brand: 'Apple', type: 'phone' },
  { name: 'Apple Watch', brand: 'Apple', type: 'watch' },
  { name: 'Galaxy S6', brand: 'Samsung', type: 'phone' },
  { name: 'Galaxy Gear', brand: 'Samsung', type: 'watch' },
]);

const unique = collection.unique(item => item.brand + item.type);

unique.all();

// [
//   { name: 'iPhone 6', brand: 'Apple', type: 'phone' },
//   { name: 'Apple Watch', brand: 'Apple', type: 'watch' },
//   { name: 'Galaxy S6', brand: 'Samsung', type: 'phone' },
//   { name: 'Galaxy Gear', brand: 'Samsung', type: 'watch' },
// ]

52 .

Explain unless() methods in Collect.js.

unless() : The unless() method will execute the given callback when the first argument given to the method evaluates to false:

const collection = collect([1, 2, 3]);

collection.unless(false, items => items.push(4));

collection.all();

// [1, 2, 3, 4]

unlessEmpty() : Alias for the whenNotEmpty() method

unlessNotEmpty() : Alias for the whenEmpty() method

53 .

Explain when() methods in Collect.js?

when() : The when() method will execute the given callback when the first argument given to the method evaluates to true:

const collection = collect([1, 2, 3]);

collection.when(true, items => items.push(4));

collection.all();

// [1, 2, 3, 4]

whenEmpty() : The whenEmpty() method will execute the given callback when the collection is empty:

const collection = collect([]);

collection.whenEmpty(c => c.push('Mohamed Salah'));

collection.all();

// ['Mohamed Salah']
const collection = collect(['Darwin Núñez']);

collection.whenEmpty(
  c => c.push('Mohamed Salah'),
  c => c.push('Xherdan Shaqiri'),
);

collection.all();

// [
//   'Darwin Núñez',
//   'Xherdan Shaqiri',
// ];

whenNotEmpty() : The whenNotEmpty() method will execute the given callback when the collection is not empty:

const collection = collect(['Darwin Núñez']);

collection.whenNotEmpty(c => c.push('Mohamed Salah'));

collection.all();

// [
//   'Darwin Núñez',
//   'Mohamed Salah',
// ]
const collection = collect(['Darwin Núñez']);

collection.whenNotEmpty(
  c => c.push('Mohamed Salah'),
  c => c.push('Xherdan Shaqiri'),
);

collection.all();

// [
//   'Darwin Núñez',
//   'Mohamed Salah',
// ];

54 .

What is the where() method in Collect.js?

where() : The where() method filters the collection by a given key / value pair:

const collection = collect([
  { product: 'Desk', price: 200, discounted: true },
  { product: 'Chair', price: 100, discounted: true },
  { product: 'Bookcase', price: 150, discounted: true },
  { product: 'Door', price: 100 },
]);

const filtered = collection.where('price', 100);

filtered.all();

// [
//   { product: 'Chair', price: 100 },
//   { product: 'Door', price: 100 },
// ]

const discounted = collection.where('discounted');

discounted.all();

// [
//  { product: 'Desk', price: 200, discounted: true },
//  { product: 'Chair', price: 100, discounted: true },
//  { product: 'Bookcase', price: 150, discounted: true },
// ]

const notDiscounted = collection.where('discounted', false);

discounted.all();

// [
//  { product: 'Door', price: 100 },
// ]

When working with nested objects where() method allows dot notated keys. E.g. where('product.category', 'office-supplies') The where method also allows for custom comparisons:

Non-identity / strict inequality (!==) :

const filtered = collection.where('price', '!==', 100);

filtered.all();

// [
//   { product: 'Desk', price: 200 },
//   { product: 'Bookcase', price: 150 },
// ]

Less than operator (<) :

const filtered = collection.where('price', '<', 100);

filtered.all();

// []

Less than or equal operator (<=) :

const filtered = collection.where('price', '<=', 100);

filtered.all();

// [
//   { product: 'Chair', price: 100 },
//   { product: 'Door', price: 100 },
// ]

Greater than operator (>) :

const filtered = collection.where('price', '>', 100);

filtered.all();

// [
//   { product: 'Desk', price: 200} ,
//   { product: 'Bookcase', price: 150 },
// ]

Greater than or equal operator (>=) :

const filtered = collection.where('price', '>=', 150);

filtered.all();

// [
//   { product: 'Desk', price: 200} ,
//   { product: 'Bookcase', price: 150 },
// ]