ts-core

Core library for TypeScript inspired by Elm. It contains only some of the more relevant data structures and functions.

Part of the Hiraeth collection.

Installation

npm install --save-dev @eeue56/ts-core

Testing

npm run build
npm run test

Usage

Basics

See src

Some useful tools for functional programming - piping, and composing. Both of these can be used to chain functions.

import { Basics } from '@eeue56/ts-core';

// take an argument then pipe it to a variable number of functions
// for example this is 10
const doubleLength = Basics.pipe(
    'hello',
    (str: string) => {
        return str.length;
    },
    (length: number) => {
        return length + length;
    }
);

// a function that turns composes each function given as an argument
const func = Basics.compose(
    (str: string) => {
        return str.length;
    },
    (length: number) => {
        return length + length;
    }
);

// this is 10
const anotherDoubleLength = func('hello');
console.log('Expecting 10', anotherDoubleLength);

Debug

See src

Not particularly useful in JS as impurity doesn't matter, but sometimes it's nice to log what you're returning.

import { Debug } from '@eeue56/ts-core';

// returns the same object as was logged
function getSomeObject(someObject){
    return Debug.log("My name is", someObject);
}

Maybe

See src

A Maybe/Optional type. Useful for when dealing with a value that can either be a value, or nothing.

import { Maybe } from '@eeue56/ts-core';

const someNothingMaybe = Maybe.Nothing();
const aValueOfZeroFromTheMaybe = Maybe.withDefault(0, someNothingMaybe);

const identity = (x) => x;
const someJustMaybe = Maybe.Just(10);
const newMaybe = Maybe.map(identity, someJustMaybe);
const aValueOfTenFromTheMaybe = Maybe.withDefault(0, someJustMaybe);

Result

See src

A Result type. Useful for when dealing with a value that can either be a value, or an error.

import { Result } from '@eeue56/ts-core';

const someResult = Result.Ok(10);
const double = (x) => x + x;
const newResult = Result.map(double, someResult);
const someResultValue = Result.withDefault(0, newResult);

const someError = Result.Err("Failed to parse on line 10");
const strLength = (x) => x.length;
const newError = Result.mapError(strLength, someError);

const someStringResult = Result.Ok("Hello");
const hello = Result.either(someStringResult);
const failedToParseOnLine10 = Result.either(someError);

Tuple

See src

A Tuple type of size 2. Useful for combining a pair of values. Generally named objects are more useful than Tuples, however.

import { Tuple } from '@eeue56/ts-core';

const someTuple = Tuple.pair(10, "okay");
const someNewTuple = Tuple.mapFirst(double, someTuple);
const someOtherTuple = Tuple.mapSecond(strLength, someTuple);
const someFirstValue = Tuple.first(someOtherTuple);
const someSecondValue = Tuple.second(someOtherTuple);