Collection Methods

every

Checks if predicate returns truthy for all element of collection.

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
predicate	Function	The function invoked per iteration.

Returns

Type	Description
boolean	Returns true if all elements pass the predicate check, else false.

Declaration

declare function every<T extends ArrayLike<any>>(
  collection: T,
  predicate: (value: ArrayLikeValue<T>, index: number, collection: T) => boolean
): boolean;
declare function every<T extends Dictionary<any>>(
  collection: T,
  predicate: (value: DictionaryValue<T>, key: string, collection: T) => boolean
): boolean;

Examples

const arr = [1, 2, 5];
every(arr, (value) => value < 10); // true

const obj = { a: 1, b: 2 };
every(arr, (_, key) => key !== 'a'); // false

filter

Iterates over elements of collection, returning an array of all elements predicate returns truthy for

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over
predicate	Function	The function invoked per iteration

Returns

Type	Description
any[]	Returns the new filterd array

Declaration

declare function filter<T extends ArrayLike<any>>(
  collection: T,
  predicate: (value: ArrayLikeValue<T>, index: number, collection: T) => boolean
): ArrayLikeValue<T>[];
declare function filter<T extends Dictionary<any>>(
  collection: T,
  predicate: (value: DictionaryValue<T>, key: string, collection: T) => boolean
): DictionaryValue<T>[];

Examples

const arr = [1, 2, 3];
filter(arr, (value, index) => index === 1); // [1, 3]

const obj = { a: 1, b: 'str' };
filter(obj, (value, key) => typeof value === 'string'); // ['str']

find

Iterates over elements of collection, returning the first element predicate returns truthy for.

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
predicate	Function	The function invoked per iteration.

Returns

Type	Description
boolean	Returns the matched element, else undefined.

Declaration

declare function find<T extends ArrayLike<any>>(
  collection: T,
  predicate: (value: ArrayLikeValue<T>, index: number, collection: T) => boolean
): ArrayLikeValue<T> | undefined;
declare function find<T extends Dictionary<any>>(
  collection: T,
  predicate: (value: DictionaryValue<T>, key: string, collection: T) => boolean
): DictionaryValue<T> | undefined;

Examples

const arr = [1, 2, 13];
find(arr, (value) => value > 10); // 13

const obj = { a: 1, b: 2 };
find(arr, (_, key) => key === 'c'); // undefined

forEach

Iterates over elements of collection and invokes iteratee for each element.

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
callback	Function	The function invoked per iteration.

Declaration

declare function forEach<T extends ArrayLike<any>>(
  collection: T,
  callback: (value: ArrayLikeValue<T>, index: number, collection: T) => void
): void;
declare function forEach<T extends Dictionary<any>>(
  collection: T,
  callback: (value: DictionaryValue<T>, key: string, collection: T) => void
): void;

Examples

const arr = [1];
forEach(arr, (value, index) => console.log(value, index)); // 1, 0

const obj = { a: 1 };
forEach(obj, (value, key) => console.log(value, key)); // 1, 'a'

forEachRight

Iterates over elements of collection and invokes iteratee for each element.

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
callback	Function	The function invoked per iteration.

Declaration

declare function forEachRight<T extends ArrayLike<any>>(
  collection: T,
  callback: (value: ArrayLikeValue<T>, index: number, collection: T) => void
): void;
declare function forEachRight<T extends Dictionary<any>>(
  collection: T,
  callback: (value: DictionaryValue<T>, key: string, collection: T) => void
): void;

Examples

const arr = [1];
forEachRight(arr, (value, index) => console.log(value, index)); // 1, 0

const obj = { a: 1 };
forEachRight(obj, (value, key) => console.log(value, key)); // 1, 'a'

groupBy

Iterates over elements of collection and invokes iteratee for each element.

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
callback	Function	The function invoked per iteration.

Returns

Type	Description
object[]>	Returns new grouped array

Declaration

declare function groupBy<T extends ArrayLike<any>>(
  collection: T,
  callback: (value: ArrayLikeValue<T>, index: number, collection: T) => string
): Record<string, ArrayLikeValue<T>[]>;
declare function groupBy<T extends Dictionary<any>>(
  collection: T,
  callback: (value: DictionaryValue<T>, key: string, collection: T) => string
): Record<string, DictionaryValue<T>[]>;

Examples

const students = [
  { name: 'john', class: 'A', score: 100 },
  { name: 'alice', class: 'B', score: 91 },
  { name: 'smith', class: 'C', score: 65 },
  { name: 'gale', class: 'A', score: 74 },
];

const results = groupBy(students, (value) =>
  value.score < 70 ? 'fail' : 'pass'
);
results.fail; // [{ name: 'smith', class: 'C', score: 65 }]
results.pass.length; // 3

map

Iterates over elements of collection and invokes iteratee for each element.

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
callback	Function	The function invoked per iteration.

Returns

Type	Description
any[]	Returns the new mapped array.

Declaration

declare function map<T = any, O extends ArrayLike<any> = ArrayLike<any>>(
  collection: O,
  callback: (value: ArrayLikeValue<O>, index: number, collection: O) => T
): T[];
declare function map<T = any, O extends Dictionary<any> = Dictionary<any>>(
  collection: O,
  callback: (value: DictionaryValue<O>, key: string, collection: O) => T
): T[];

Examples

const arr = [1, 2, 3];
map(arr, (value, index) => value + index); // [1, 3, 5]

const obj = { a: 1, b: 2, c: 3 };
map(obj, (value, key) => value + key); // ['a1', 'b2', 'c3']

reduce

Executes a user-supplied "reducer" callback function on each element of the array, in order, passing in the return value from the calculation on the preceding element. The final result of running the reducer across all elements of the array is a single value.

The first time that the callback is run there is no "return value of the previous calculation". If supplied, an initial value may be used in its place. Otherwise the collection's first element is used as the initial value

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
reducer	Function	The function invoked per iteration.
[accumulator]	any	The initial value.

Returns

Type	Description
any	Returns the accumulated value.

Declaration

declare function reduce<T extends ArrayLike<any> = ArrayLike<any>>(
  collection: T,
  reducer: (
    accumulator: ArrayLikeValue<T>,
    value: ArrayLikeValue<T>,
    index: number,
    collection: T
  ) => ArrayLikeValue<T>,
  accumulator?: ArrayLikeValue<T>
): ArrayLikeValue<T>;
declare function reduce<T extends ArrayLike<any> = ArrayLike<any>, V = any>(
  collection: T,
  reducer: (
    accumulator: V,
    value: ArrayLikeValue<T>,
    index: number,
    collection: T
  ) => V,
  accumulator: V
): V;
declare function reduce<T extends Dictionary<any> = Dictionary<any>>(
  collection: T,
  reducer: (
    accumulator: DictionaryValue<T>,
    value: DictionaryValue<T>,
    key: string,
    collection: T
  ) => DictionaryValue<T>,
  accumulator?: DictionaryValue<T>
): DictionaryValue<T>;
declare function reduce<T extends Dictionary<any> = Dictionary<any>, V = any>(
  collection: T,
  reducer: (
    accumulator: V,
    value: DictionaryValue<T>,
    key: string,
    collection: T
  ) => V,
  accumulator: V
): V;

Examples

const arr = [1, 2, 3];
reduce(arr, (acc, value) => `${acc}_${value}`, ''); // '_1_2_3'

reduceRight

Executes a user-supplied "reducer" callback function on each element of the array, in order, passing in the return value from the calculation on the preceding element. The final result of running the reducer across all elements of the array is a single value.

The first time that the callback is run there is no "return value of the previous calculation". If supplied, an initial value may be used in its place. Otherwise the collection's last element is used as the initial value

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
reducer	Function	The function invoked per iteration.
[accumulator]	any	The initial value.

Returns

Type	Description
any	Returns the accumulated value.

Declaration

declare function reduceRight<T extends ArrayLike<any> = ArrayLike<any>>(
  collection: T,
  reducer: (
    accumulator: ArrayLikeValue<T>,
    value: ArrayLikeValue<T>,
    index: number,
    collection: T
  ) => ArrayLikeValue<T>,
  accumulator?: ArrayLikeValue<T>
): ArrayLikeValue<T>;
declare function reduceRight<
  T extends ArrayLike<any> = ArrayLike<any>,
  V = any,
>(
  collection: T,
  reducer: (
    accumulator: V,
    value: ArrayLikeValue<T>,
    index: number,
    collection: T
  ) => V,
  accumulator: V
): V;
declare function reduceRight<T extends Dictionary<any> = Dictionary<any>>(
  collection: T,
  reducer: (
    accumulator: DictionaryValue<T>,
    value: DictionaryValue<T>,
    key: string,
    collection: T
  ) => DictionaryValue<T>,
  accumulator?: DictionaryValue<T>
): DictionaryValue<T>;
declare function reduceRight<
  T extends Dictionary<any> = Dictionary<any>,
  V = any,
>(
  collection: T,
  reducer: (
    accumulator: V,
    value: DictionaryValue<T>,
    key: string,
    collection: T
  ) => V,
  accumulator: V
): V;

Examples

const arr = [1, 2, 3];
reduceRight(arr, (acc, value) => `${acc}_${value}`, ''); // '_3_2_1'

some

Checks if predicate returns truthy for any element of collection.

Since: 0.1.0

Arguments

Param	Type	Description
collection	Collection	The collection to iterate over.
predicate	Function	The function invoked per iteration.

Returns

Type	Description
boolean	Returns true if any element passes the predicate check, else false.

Declaration

declare function some<T extends ArrayLike<any>>(
  collection: T,
  predicate: (value: ArrayLikeValue<T>, index: number, collection: T) => boolean
): boolean;
declare function some<T extends Dictionary<any>>(
  collection: T,
  predicate: (value: DictionaryValue<T>, key: string, collection: T) => boolean
): boolean;

Examples

const arr = [1, 2, 13];
some(arr, (value) => value > 10); // true

const obj = { a: 1, b: 2 };
some(arr, (_, key) => key === 'c'); // false