t-fp-assoc

Simple Functional assoc function that can be used against typed Interfaces or loose KV pairs.

Types

The following function signatures exist:

export interface Assoc {
    <Ob, K extends keyof Ob>(k: K, v: Ob[K], a: Ob): Ob;
    <A, B>(k: string, v: A, ob: {[k: string]: B}): {[k: string]: B|A};
    <Ob, V, K extends keyof Ob>(k: string, v: V, a: Ob): Ob & {[k: string]: Ob[K]|V};
}

Usage - Interfaces

import assoc from 't-fp-assoc-single-type';
interface XX { a: string; b: number; };

let xx1: XX = {a: 'str', b: -1};
let xx2: XX = assoc('b', 10, xx1);
let result = assoc('b', 10, xx2);

The type for result is XX.

Usage - Extended Interface

import assoc from 't-fp-assoc-single-type';
interface XX { a: string; b: number; };

let xx1: XX = {a: 'str', b: -1};
let result = assoc('c', null, xx1);

The type for result is XX & { [k: string]: string | number | null; }

Usage - KV Pairs

import assoc from 't-fp-assoc';

let input: {[k: string]: number} = {b: 2};
let result = assoc('a', 'one', input); // {a: 'one', b: 2}

The type for result is { [k: string]: string | number }.

Installation

Use npm install t-fp-assoc to install.