ts-utility-functions

Utility functions for TypeScript

Installation

npm install ts-utility-functions

Usage

String

str.is

str.is('')          // true
str.is(123)         // false
vals.filter(str.is) // filter out non-string values

str.isStartWith

str.isStartWith('abc')('a')       // true
str.isStartWith('abc')('b')       // false
vals.filter(str.isStartWith('a')) // filter out values that do not start with 'a'

Types

assert.type, assert.never

import { assert } from 'ts-utility-functions';

// assert.type
type Currency = 'USD' | 'EUR';
const currency: Currency = 'USD';

switch (currency) {
  case 'USD':
    break;
  case 'EUR':
    break;
  default:
    assert.type<never>(currency); // compilation - ok, runtime - ok
    assert.never(currency);       // compilation - ok, runtime - ok
}

switch (currency) {
  case 'USD':
    break;
  default:
    assert.type<never>(currency); // compilation - error, runtime - ok
    assert.never(currency);       // compilation - error, runtime - ok
}

Object

obj.copyIntersectingFields

const a = { a: 1, b: 2, c: 3 }
const b = { a: 0, b: 0 }
copyIntersectingFields(a, b, ['a', 'b'])
console.log(b) // { a: 1, b: 2 }

obj.copyIntersectingFields.toNew

const a = { a: 1, b: 2, c: 3 }
class B {
  constructor(public a: number, public b: number) {}
}
const b = copyIntersectingFields.toNew(a, B, ['a', 'b'])
console.log(b) // A { a: 1, b: 2 }

obj.merge

const a = { a: 1, b: 2 }
const b = { b: 3, c: 4 }
const c = { c: 5, d: 6 }
const d = merge(a, b, c)
console.log(d) // { a: 1, b: 3, c: 5, d: 6 }

obj.vals

const a = { a: 1, b: 2, c: '3' }
const b = vals(a)
console.log(b) // [1, 2, '3'] as (string | number)[]

const a = { a: 1, b: 2, c: '3' } as const
const b = vals(a)
console.log(b) // [1, 2, '3'] as (1 | 2 | '3')[]

obj.keys

const a = { a: 1, b: 2, c: 3 }
const b = keys(a)
console.log(b) // ['a', 'b', 'c'] as ('a', 'b', 'c')[]

Function

fn.noop

const a = fn.noop() // does nothing (returns undefined)

fn.noopAsync

const a = await fn.noopAsync() // does nothing (returns Promise<undefined>)

Array

arr.is

arr.is([])          // true
arr.is([1, 2, 3])   // true
vals.filter(arr.is) // filter out non-array values

arr.isNot

arr.isNot([])          // false
arr.isNot([1, 2, 3])   // false
vals.filter(arr.isNot) // filter out array values

arr.req

arr.req([])          // []
arr.req([1, 2, 3])   // [1, 2, 3]
arr.req(null)        // throws error

arr.isEmpty

arr.isEmpty([])          // true
arr.isEmpty([1, 2, 3])   // false
vals.filter(arr.isEmpty) // filter out non-empty arrays

arr.isNotEmpty

arr.isNotEmpty([])          // false
arr.isNotEmpty([1, 2, 3])   // true
vals.filter(arr.isNotEmpty) // filter out empty arrays

arr.isEmptySafe

arr.isEmptySafe([])          // true
arr.isEmptySafe(null)        // true
arr.isEmptySafe(undefined)   // true
arr.isEmptySafe([1, 2, 3])   // false
vals.filter(arr.isEmptySafe) // filter out non-empty arrays

arr.isNotEmptySafe

arr.isNotEmptySafe([])          // false
arr.isNotEmptySafe(null)        // false
arr.isNotEmptySafe(undefined)   // false
arr.isNotEmptySafe([1, 2, 3])   // true
vals.filter(arr.isNotEmptySafe) // filter out empty arrays