TypeScript Immutable Utils

Type-safe immutability helpers for simple objects and arrays.

Installation

npm install --save typescript-immutable-utils

API

Arrays

• setAt<T>(items: T[], index: number, item: T): T[]

  Returns new array with replaced item at given index.

  If item is equal to the old one, original array is returned.

• insertAt<T>(items: T[], index: number, item: T): T[]

  Returns new array with inserted item at given index.

  If index is negative, counts from the end of the array.

• removeAt<T>(items: T[], index: number): T[]

  Returns new array with removed item at given index.

  If index is out of bounds, original array is returned.

  If index is negative, counts from the end of the array.

• removeValue<T>(items: T[], item: T): T[]

  Returns new array with given value removed.

  If value is not present in the array, it is returned unchanged.

Objects

• update<T>(target: T, values: Partial<T>): T

  Returns new object with updated values.

  If all values are the same, original object is returned.

Maps (ES-2015)

• mapValues<K, T, R>(src: Map<K, T>, map: (value: T, key: K) => R): Map<K, R>

  Returns new Map with updated values

Dicts

Dictionary type is a simple index signature:

type Dict<V> = {[key: string]: V};

• createDict<V>(): Dict<V>

  Creates empty dict.

• copyDict<V>(dict: Dict<V>): Dict<V>

  Copies given dict.

• hasKey(dict: Dict<any>, key: any): boolean

  Checks whether dict has given key.

• mapValues<T, R>(dict: Dict<T>, map: (value: T) => R): Dict<R>

  Creates new dict with same keys as given dict whose values are the result of applying mapping function on given dict values.

  If every returned value is the same as in original dict, original dict is returned.

• union<V>(target: Dict<V>, source: Dict<V>): Dict<V>

  Creates new dict with values from both given dicts.

• setKey<V>(dict: Dict<V>, key: any, value: V): Dict<V>

  Returns new dict with given key set to given value.

  If the value is the same as in original dict, original dict is returned.

• removeKey<V>(dict: Dict<V>, ...keys: any[]): Dict<V>

  Returns new dict with given keys removed.

  If none of the keys are present in original dict, original dict is returned.

• fromKeys<V>(keys: any[], values: V | ((key: any) => V)): Dict<V>

  If values is not a function, creates new dict with given keys whose values are all the same and equal to values.

  If values is function, creates new dict with given keys whose values are the result of applying this function to the key.