linqjs

Some LINQ functionality for JavaScript Array

Installation

npm install lqjs

Supplies the following functions for arrays:

• all
• any
• copy
• distinct
• first
• orderBy
• orderByDescending
• select
• skip
• take
• where

Say you have the following array:

let people = [
  { name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' },
  { name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' },
  { name: 'Britney Spears', age: 35, isAlive: true, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' },

  // Yes I know she is added twice, it's for the distinct() call!
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' }
];

all

Determines whether all elements of a sequence satisfy a condition.

Param: Function predicate

Returns: boolean

Example:

let allIsAlive = people.all(x => x.isAlive);

Will produce:

false

any

Determines whether any element of a sequence satisfies a condition.

Param: Function predicate

Returns: boolean

Example:

let females = people.any(x => x.gender === 'F');

Will produce:

true

copy

Make an exact copy of the array, not a reference.

Param none

Returns: Array

Example:

let copiedList = people.copy();

Will produce:

[
  { name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' },
  { name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' },
  { name: 'Britney Spears', age: 35, isAlive: true, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' }
]

distinct

Returns distinct elements from a sequence.

Param: none

Returns: Array

Example:

let distinctList = people.distinct();

Will produce:

[
  { name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' },
  { name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' },
  { name: 'Britney Spears', age: 35, isAlive: true, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' }
]

first

Returns the first element of a sequence based on a predicate, or a null if the sequence contains no elements. I've combined First(), FirstOrDefault(), Single(), and SingleOrDefault() into first(), and all "fails" just return a null.

Param: Function predicate

Returns: Object

Examples:

let khan = people.first(x => x.name.endsWith('Khan'));

Will produce:

{ name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' }

let obama = people.first();

Will produce:

{ name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' }

let nonExisting = people.first(x => x.age === 100);

Will produce:

null

orderBy

Sorts the elements of a sequence in ascending order according to a key.

Param: string key

Returns: Array

Example:

let alphabetically = people.orderBy('name');

Will produce:

[
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' },
  { name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' },
  { name: 'Britney Spears', age: 35, isAlive: true, gender: 'F' },
  { name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' }
]

orderByDescending

Sorts the elements of a sequence in descending order.

Param: string key

Returns: Array

Example:

let unalphabetically = people.orderByDescending('name');

Will produce:

[
  { name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' },
  { name: 'Britney Spears', age: 35, isAlive: true, gender: 'F' },
  { name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' }
]

select

Projects each element of a sequence into a new form.

Param: Object map

Returns: Array

Example:

let firstNamesAndGender = people.select({
  firstName: x => x.name.substr(0, x.name.indexOf(' ')),
  gender: x => x.gender === 'M' ? 'Male' : 'Female'
});

Will produce:

[
  { firstName: 'Barack', gender: 'Male' },
  { firstName: 'Genghis', gender: 'Male' },
  { firstName: 'Britney', gender: 'Female' },
  { firstName: 'Ada', gender: 'Female' },
  { firstName: 'Ada', gender: 'Female' }
]

skip

Bypasses a specified number of elements in a sequence and then returns the remaining elements.

Param: int number

Returns: Array

Example:

let skipped = people.skip(2);

Will produce:

[
  { name: 'Britney Spears', age: 35, isAlive: true, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' },
  { name: 'Ada Lovelace', age: 36, isAlive: false, gender: 'F' }
]

take

Returns a specified number of contiguous elements from the start of a sequence.

Param: int number

Returns: Array

Example:

let taken = people.take(2);

Will produce:

[
  { name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' },
  { name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' }
]

where

Filters a sequence of values based on a predicate.

Param: Function predicate

Returns: Array

Example:

let wheres = people.where(x => x.age > 50);

Will produce:

[
  { name: 'Barack Obama', age: 55, isAlive: true, gender: 'M' },
  { name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' }
]

chains

You can chain multiple functions as they're prototypes of the Array object.

Examples:

let names = people
  .orderBy('name')
  .skip(2)
  .take(2)
  .where(x => x.age < 40);

Will produce:

[
  { name: 'Britney Spears', age: 35, isAlive: true, gender: 'F' }
]

let otherPerson = people
  .where(x => !x.isAlive &&
              x.gender === 'M')
  .first();

Will produce:

{ name: 'Genghis Khan', age: 65, isAlive: false, gender: 'M' }