my-easy-fp

Simple functional programming utility & programming helper tools

Simple utility functions that can use browser, node.

Function list

boolean

name	description
isFalse	If argument false, return true
isTrue	If argument true, return true
invert	return inverted boolean value

array

name	description
populate	populate array zero base, if you pass second argument true that populate one base
chunk	array split given size
last	pick last element from array
first	pick first element from array
toArray	make array given argument
settify	make it set and convert it back to array

empty

name	description
isUndefined	if argument undefiend, return true
isNotUndefined	if argument not undefined, return true
isNull	if argument null, return true
isNotNull	if argument not null, return true
isNotEmpty	if argument not null and undefined, return true
isEmpty	if argument null or undefined, return true
isComplexEmpty	if argument not undefined and null, do additional test isNaN, empty string, empty array, empty object
isNotComplexEmpty	return inverted value isComplexEmpty

misc

name	description
typedkey	same work Object.keys, but typed key in Recoed
getRandomRange	return random value in min and max
getRandomRangeInt	return random integer value in min and max
isError	if argument is Error return Error or return undefined

sleep

name	description
sleep	sleep given millisecond

Custom Utility Types

name	description
TResolvePromise	get type resolved promise
TResolveArray	get type resolve array
TNullablePick	convert specific field to nullable
TNonNullableObject	object type each field to non nullable
TNonNullablePick	convert specific field to non nullable

False & True checker

Why need this utility?

import { isFalse } from 'my-easy-fp';

const iamboolean = false;

// this line easily miss in refactoring or changing
if (!iamboolean) {
  console.log('I am execute false-case');
}

// more than better!
if (isFalse(iamboolean)) {
  console.log('I am execute false-case');
}

Empty checker

Why need this utility?

const iamempty?: string | null = undefined;

// this line some boring task
if (iamempty === undefined || iamempty === null || iamempty !== '') {
  console.log('i am empty');
}

// more than better!
if (isComplexEmpty(iamempty)) {
  console.log('i am empty');
}

You need only undefined and null check, use double equal operator.

const iamempty?: string | null = undefined;

// Recently ESLint allow double equal for null check
// see https://eslint.org/docs/latest/rules/eqeqeq#allow-null
if (iamempty == null) {
  console.log('i am empty');
}

Sleep

Why need this utility?

const ms = 1000;

// this line some boring task
await new Promise((resolve) => setTimeout(() => resolve(), ms));

// more than better!
await sleep(ms);

Array

populate, chunk utility here.

// seq is [0,1,2,3,4,5,6,7,8,9]
const seq = populate(10);

// seq is [1,2,3,4,5,6,7,8,9,10]
const seq = populate(10, true);

// chunked is [[1,2],[3,4],[5,6],[7]]
const chunked = chunk([1, 2, 3, 4, 5, 6, 7], 2);

// settify is [ 1, 2, 3, 4 ]
const settified = settify([1, 1, 2, 3, 2, 3, 4]);

// zeroIndex is 1
const zeroIndex = atOrThrow([1, 2, 3], 0);

Type Helper

resolve promise, array. But you can use type-fest or ts-essentials. Recommand use type-fest and tsessentials.

// you can get string | Buffer type
type TResolvedPromiseType = TResolvePromise<ReturnType<typeof fs.promises.readFile>>;

// you can get number type
type TResolvedArrayType = TResolveArray<number[]>;

interface IStudent {
  name: string;
  major: string;
  grade: number;
}

// you can get { name?: string; major?: string; grade: number; }
// converted Omit<IStudent, 'name' | 'major'> & Pick<Partial<IStudent>, 'name' | 'major'>
type TCliArgumentStudent = TNullablePick<IStudent, 'name' | 'major'>;