Type Utils

[npm]: https://npmjs.com/package/@srhenry/type-utils

> Type utilities module for Typescript and also Javascript. It can secure your application from invalid data being pushed inside and breaking things as it can shape and model your data to prevent invalid data. Check out the documentation for further details.

Table of Contents

- Type Utils
- Table of Contents
- Installing
- Docs
- Schema types
- Schema.string
- Schema.number
- Schema.boolean
- Schema.object
- Schema.array
- Schema.symbol
- Schema.asEnum
- Schema.asNull
- Schema.primitive
- Schema.any
- Schema.optional
- Schema helpers
- Schema.and
- Schema.or
- Schema.useSchema
- Validation rules
- Number.nonZero
- Number.max
- Number.min
- Array.max
- Array.min
- Array.unique
- String.max
- String.min
- String.regex
- String.nonEmpty
- String.url
- String.email
- Record.nonEmpty
- Schema.use
- Available validations
- is
- ensureInterface
- Match Pattern
-match()
- Util types
- Fn
- AsyncFn
- Action
- Predicate
- Result
- AsyncResult
- TupleSlice
- Param
- Infer
- Experimental Features
- Lambda
- Function/Lambda Currying
- Pipelines/Pipes
- Switch Expression
- Reusable switcher
- Stored switcher
- more complex matching logic / runtime branch evaluation

Installing

With NPM:

``bash
npm install @srhenry/type-utils --save
`

With Yarn:

`bash
yarn add @srhenry/type-utils
`

Docs

> See: API - Github Pages

$3

#### Schema.string

It represents a string to typescript's type infers and runtime validation

`typescript
import { string } from '@srhenry/type-utils'

const isString = string() //any string
const isAvocadoString = string('avocado') //specific string
const isPatternString = string(/goo+gle/) //pattern/RegExp matched string
`

#### Schema.number

It represents a number to typescript's type infers and runtime validation

`typescript
import { number } from '@srhenry/type-utils'

const isNumber = number()
`

#### Schema.boolean

It represents a number to typescript's type infers and runtime validation

`typescript
import { boolean } from '@srhenry/type-utils'

const isBoolean = boolean()
`

#### Schema.object

It represents a well defined object to typescript's type infers and runtime validation, which its properties are also described using the Schema helpers

`typescript
import { object, string, number } from '@srhenry/type-utils'

const isMyObject = object({
foo: string(),
bar: number(),
})
`

#### Schema.array

It represents an array to typescript's type infers and runtime validation, which its items can also be described using the Schema helpers

`typescript
import { array, string, object } from '@srhenry/type-utils'

const isArray = array() // array of anything
const isMyArray = array(string()) // array of strings
const isMyObjArray = array(object({ foo: string('bar') }))
const isMyObjArray2 = array({ foo: string('bar') })
`

#### Schema.symbol

It represents a symbol to typescript's type infers and runtime validation

`typescript
import { symbol } from '@srhenry/type-utils'

const isSymbol = symbol()
`

#### Schema.asEnum

It represents a closed switch values to typescript's type infers and runtime validation. It ensures your value is one of the values given in params.

`typescript
import { asEnum } from "@srhenry/type-utils"

enum Status {
ready: 1,
running: 2,
stopped: 3,
}

const validStatus = [...Object.keys(Status)] as (keyof typeof Status)[]

const isStatus = asEnum(validStatus)
`

#### Schema.asNull

It represents a null literal to typescript's type infers and runtime validation.

`typescript
import { asNull } from '@srhenry/type-utils'

const isNull = asNull()
`

#### Schema.primitive

It represents a primitive values (such as string, number, boolean, symbol, null, undefined) to typescript's type infers and runtime validation.

`typescript
import { primitive } from '@srhenry/type-utils'

const isSymbol = primitive()
`

#### Schema.any

It represents a 'any' value to typescript's type infers and runtime validation. It does nothing to validate a narrowed type but can be useful to improve readability in more complex schemas.

`typescript
import { any, object } from '@srhenry/type-utils'

const isAny = any()
const objectHasFoo = object({ foo: isAny }) //it checks if is object and if has foo property but doesn't care checking its type
`

#### Schema.optional

> Since v0.5.0, this method was removed, but also embeded in all exported schemas.

> Since v0.6.0, this method was replaced to be a property in the returned type guard instead of a property of the schema.

It represents a optional value to typescript's type infers and runtime validation. You can access this schema by acessing the .optional property in the desired optional schema:

`typescript
import { object, string, number } from '@srhenry/type-utils'

const objectMaybeHasFoo = object({
foo: string().optional(),
bar: number().optional()
})
// it checks if is object and if has foo.
// if it has foo then check if it is string or undefined,
// if it hasn't then pass anyway as it is optional property.
`

$3

#### Schema.and

It creates an intersection between two schemas.

`typescript
import { object, string, and } from '@srhenry/type-utils'

const hasFoo = object({ foo: string() })
const hasBar = object({ bar: string() })
const isSomething = and(hasFoo, hasBar)
`

#### Schema.or

It creates an union between two schemas.

`typescript
import { string, boolean, or } from '@srhenry/type-utils'

const isString = string()
const isBool = boolean()
const isSomething = or(isString, isBool)
`

#### Schema.useSchema

It wraps a schema (just to improve readability).

`typescript
import { object, string, array, useSchema } from '@srhenry/type-utils'

const hasFoo = object({ foo: string() })
const isFooArray = array(useSchema(hasFoo))
`

$3

#### Number.nonZero

It constraints a number to be different from 0.

`typescript
import { number } from '@srhenry/type-utils'

const isNonZeroNumber = number().nonZero()
`

#### Number.max

It constraints a number to be lesser than a given number.

`typescript
import { number } from '@srhenry/type-utils'

const isNonZeroNumber = number().max(255)
`

#### Number.min

It constraints a number to be greater than a given number.

`typescript
import { number } from '@srhenry/type-utils'

const isNonZeroNumber = number().min(1)
`

#### Array.max

It constraints an array's size to be lesser than a given number.

`typescript
import { array, any } from '@srhenry/type-utils'

const isArray = array(any()).max(25)
`

#### Array.min

It constraints an array's size to be greater than a given number.

`typescript
import { array, any } from '@srhenry/type-utils'

const isArray = array(any()).min(2)
`

#### Array.unique

It constraints an array to contain only distinct values, failling if a duplicate is found.

`typescript
import { array, string } from '@srhenry/type-utils'

const isArray = array(string()).unique()
`

#### String.max

It constraints a string's size to be lesser than a given number.

`typescript
import { string } from '@srhenry/type-utils'

const isString = string().max(60)
`

#### String.min

It constraints a string's size to be greater than a given number.

`typescript
import { string } from '@srhenry/type-utils'

const isString = string().min(10)
`

#### String.regex

It constraints a string to match a given pattern (regular expression).

`typescript
import { string } from '@srhenry/type-utils'

const isNumericString = string(/[0-9]+/)
// or using fluent pattern:
const isNumericString2 = string().regex(/[0-9]+/)
`

#### String.nonEmpty

It constraints a string's size to be greater than 0.

`typescript
import { string } from '@srhenry/type-utils'

const isString = string().nonEmpty()
`

#### String.url

It constraints a string to be a valid url representation.

`typescript
import { string } from '@srhenry/type-utils'

const isStringUrl = string().url()
`

#### String.email

It constraints a string to be a valid email representation.

`typescript
import { string } from '@srhenry/type-utils'

const isStringEmail = string().email()
`

#### Record.nonEmpty

It constrains a record to not be empty.

`typescript
import { record } from '@srhenry/type-utils'


const isNonEmptyRecord = record().nonEmpty()
`

#### Schema.use

> Since v0.6.0

It allows you to create custom validation rules to be used in schemas.

`typescript
import { string, createRule } from '@srhenry/type-utils'

const StringNumber = createRule({
name: "Custom.StringNumber",
message: "number",
handler: (value: string) => () => !Number.isNaN(Number(value)),
});

const isStringNumber = string().use(StringNumber())
`

#### Schema.validator

> Since v0.6.1

It allows you to get a validator instance to validate a value against the schema.

`typescript
import { string, or, object, createInlineRule, createRule } from '@srhenry/type-utils'

const StringNumber = createRule({
name: "Custom.StringNumber",
message: "number",
handler: (value: string) => () => !Number.isNaN(Number(value)),
});

const isStringNumberOrObject = or(
string()
.use(createInlineRule("Custom.StringNumber", (value: string) => !Number.isNaN(Number(value)))),
object({
foo: string().use(StringNumber()),
bar: string().optional()
}));
`

$3

#### is

It checks a given value against a given schema or validator and return true if schema matches the value, otherwise return false.

`typescript
import { string, is } from '@srhenry/type-utils'

//...
if (is(value, string())) {
// value is string
} else {
// value is not a string
}
`

#### ensureInterface

It checks a given value against a given schema or validator and returns the checked value with schema inferred type if schema matches the value or throws an error if schema didn't match the value. Pretty clean to use with destructuring pattern.

`typescript
import { object, number, string, ensureInterface } from '@srhenry/type-utils'

//...
const { foo, bar } = ensureInterface(value, object({
foo: number(),
bar: string(),
}) //It throws an error if validation fails!

console.log('foo', foo) // foo
console.log('bar', bar) // bar
`

NOTE: You can use schema directly to validate a value.

`typescript
import { object, number } from "@srhenry/type-utils"

const hasFoo = object({ foo: number() }))

//...
if (hasFoo(obj)) {
// obj is object and contains a string property named foo
} else {
// obj don't have a foo property of type string
}
`

$3

#### match()

Create a new reusable pattern matcher object or an inline pattern matcher object for a given value.

Reusable matcher example:

`typescript
import { match, object, string, array, pick } from '@srhenry/type-utils'

const matcher = match()
.with(object({ foo: string().min(3) }), obj => Foo is valid: '${obj.foo}')
.with(string().nonEmpty(), str => String is valid: '${str}')
.default(() => { throw new TypeError('😭') })

matcher.exec('foo') //String is valid: 'foo'
matcher.exec({ foo: 'bar' }) //Foo is valid: 'bar'
matcher.exec({ foo: 'ba' }) //TypeError: 😭
matcher.exec("") //TypeError: 😭
`

Inline matcher example:

`typescript
import { match, object, string, array, pick } from '@srhenry/type-utils'

//API endpoint processing example:
const { data } = payload

const responses = await Promise.allSettled(
match(data)
.with(object({ events: array() }), ({ events }) => events.map(e =>
match(e)
.with(
object({ type: string("USER_EVENT"), uid: string() }),
({ type: _, uid, ...data }) => UserEvent.send({ from:uid, ...data }))
.with(
object({ type: string("SYSTEM_EVENT") }),
({ type: _, ...data }) => SystemEvent.process({ ...data }))
.default(() => null)
.exec()))
.default(() => [])
.exec()
.filter(Boolean))
.then(results =>
results.map(result => match(result)
.with(
object({ status: string("fulfilled") }),
({ value }) => parseToResponse(value))
.with(
object({ status: string("rejected") }), ({ reason }) => {
log.error('Event processing failed:', reason)
switch(reason.type) {
case 'UserEventError':
//specific handling for user event errors
return UserEventError.from(reason)
break;
case 'SystemError':
//specific handling for system event errors
return SystemError.from(reason)
break;

default:
return reason
}})
.exec()))

return new JsonResponse({ success:true, event_responses: responses }) //formatted response
`

$3

#### Fn

It represents a synchronous function type.
It has two type parameters: the first is a tuple representing the function parameters types, and the second is the return type of the function.

`typescript
import type { Fn } from '@srhenry/type-utils'

declare const fn: Fn<[number, number], number> // fn: (arg_0: number, arg_1: number) => number
`

#### AsyncFn

It represents an asynchronous function type.
It has two type parameters: the first is a tuple representing the function parameters types, and the second is the resolved return type of the function.

`typescript
import type { AsyncFn } from '@srhenry/type-utils'

declare const fn: AsyncFn<[number, number], number> // fn: (arg_0: number, arg_1: number) => Promise
`

#### Action

It represents a synchronous function type that does not return any value (void).
It has one type parameter: a tuple representing the function parameters type.

`typescript
import type { Action } from '@srhenry/type-utils'

declare const fn: Action<[string]> // fn: (arg_0: string) => void
`

#### Predicate

It represents a predicate function type.
It has one type parameter: a tuple representing the function parameters type.

`typescript
import type { Predicate } from '@srhenry/type-utils'

declare const fn: Predicate<[any]> // fn: (arg_0: any) => boolean
`

#### Result

It represents an result type tuple.
It has two type parameters: the first is the success type, and the second is the failure type (optional, default Error).

`typescript
import type { Result } from '@srhenry/type-utils'

declare const res1: Result // res1: [null, number] | [Error, null]
declare const res2: Result // res2: [null, string] | [TypeError, null]
`

#### AsyncResult

It represents an asynchronous result type tuple.
It has two type parameters: the first is the success type, and the second is the failure type (optional, default Error).

`typescript
import type { AsyncResult } from '@srhenry/type-utils'

declare const res1: AsyncResult // res1: [null, number] | [Error, null]
declare const res2: AsyncResult // res2: [null, string] | [TypeError, null]
`

#### TupleSlice

It slices a tuple type.
It has three type parameters: the first is the tuple type to be sliced, the second is the start index (inclusive), and the third is the end index (exclusive, optional, default to tuple length).

`typescript
import type { TupleSlice } from '@srhenry/type-utils'

declare const res1: TupleSlice<[number, string, boolean], 1> // res1: [string, boolean]
declare const res2: TupleSlice<[number, string, boolean], 1, 2> // res2: [string]
`

#### Param

It extracts the type of a function parameter by its index.
It has two type parameters: the first is the function type, and the second is the parameter index.

`typescript
import type { Param } from '@srhenry/type-utils'

declare const res1: Param<(a: number, b: string) => void, 0> // res1: number
declare const res2: Param<(a: number, b: string) => void, 1> // res2: string
`

#### Infer

It infers the type from a type guard function.
It has one type parameter: the type guard function type.

`typescript
import { type Infer, array } from '@srhenry/type-utils'

declare const isArray = array()

declare const res1: Infer<(a: unknown) => a is number> // res1: number
declare const res2: Infer<(a: unknown) => a is string[]> // res2: string[]
declare const res3: Infer // res3: any[]
`

Experimental Features

$3

This was inspired in C# Lambdas, equivalent to arrow functions in Javascript/Typescript, but this helper adds invoke() method to a function instance. useful to improve readability when you have a function that returns another and you wanna call 'em all in a row, using fluent pattern.

`typescript
import { Experimental } from '@srhenry/type-utils'

const { lambda } = Experimental

function builder(locales: string | string[] = 'en-US') {
function formatter(
options: Intl.DateTimeFormatOptions = {
dateStyle: 'short',
timeStyle: 'short',
}
) {
function format(date: Date | string) {
return new Intl.DateTimeFormat(locales, options).format(new Date(date))
}

return lambda(format)
}

return lambda(formatter)
}

console.log(
'1970-01-01T00:00 =',
builder('en-UK').invoke({ dateStyle: 'long' }).invoke('1970-01-01')
) // 01 January 1970
`

---

$3

This does type-wisely curries a function or lambda, in two flavors: allowing or not partial param applying (default is not allowed). The process of currying a function is traditionally a techique that allows you to call the refered function passing one parameter at a time, returning another function to further apply remaining parameters, then returning whatever the original function returns after all parameters were given to curried function. In Javascript this techinque usually allows partial apply, and in that way you can pass more than one parameter at a time, and everything else remains equal to the traditional currying.

`typescript
import { Experimental } from '@srhenry/type-utils'

const { lambda, curry } = Experimental

// lets reuse earlier example:
function builder(
locales: string | string[],
options: Intl.DateTimeFormatOptions,
date: Date | string
) {
return new Intl.DateTimeFormat(locales, options).format(new Date(date))
}

const curried = curry(builder)
const curriedLambda = curry(lambda(builder))

console.log(
curried('en-GB')({ timeStyle: 'short', timeZone: 'Etc/Greenwich' })(
new Date('2020-05-10T22:35:08Z')
)
) // 22:35

console.log(
curriedLambda('en-US')
.invoke({ dateStyle: 'short', timeStyle: 'short', timeZone: 'America/New_York' })
.invoke(new Date('2020-05-10T22:35:08Z'))
) // (EDT) 5/10/20, 6:35 PM
`

---

$3

This is a fluent API to create sync/async function pipelines. Inspired in FP pipe operator while it does not comes to Javascript/Typescript yet. It allows only single param functions, piping the return as the parameter to the next function in pipeline.

`typescript
import { Experimental } from '@srhenry/type-utils'

const { pipe, enpipe, lambda } = Experimental

const addUserFactory =
(db: Record[]>) => (user: Record) =>
new Promise(resolve => {
setTimeout(() => {
const id = uuid()

db['users'] ??= []
db['users']?.push({ id, ...user })
resolve(id)
}, 200)
})
const addPostFactory =
(db: Record[]>) => (user_id: string, post: Record) =>
new Promise(resolve => {
setTimeout(() => {
db['posts'] ??= []
db['posts']?.push({ user_id, ...post })
resolve(true)
}, 300)
})

const db = {
users: [] as Record[],
posts: [] as Record[],
} as Record[]>

const len = (s: string | ArrayLike) => s.length
const addPostCurried = (post: Record) => (id: string) =>
pipe(addPostFactory).pipe(enpipe(db)).pipe(lambda).invoke(id, post)

const result = await pipe(addUserFactory)
.pipe(enpipe(db))
.pipe(
enpipe({
name: 'Marcus',
email: 'example@email.com',
})
)
.pipeAsync(
addPostCurried({
title: 'Hello World',
content: 'Lorem ipsum dolor sit amet',
})
)
.pipeAsync(() => {
if (len(db['users']!) === 0 || len(db['posts']!) === 0) return false

db['replies'] = []
return true
})
.depipe() // true | false
`

---

$3

> @deprecated since 0.6.2.
>
> Use the new match() factory instead.

This helper enables you to build switch expressions as it is not available in Javascript vanilla. Each branch allows you to define the matchers or values ahead of time with literal values or inline expressions, or define with callbacks to customize handling of each branch, making it a powerfull way to describe a complex switch without if-else-if language syntax. It defines a lambda as the switch runner, so you can define and run it in the row with more readability.

#### Reusable switcher

`typescript
const switcher = $switch()
.case(4, 'four')
.case(3, 'three')
.case(2, 'two')
.case(1, 'one')
.default('none of the above') // it does not run yet

console.log(switcher.invoke(1)) // one
console.log(switcher.invoke(3)) // three
console.log(switcher.invoke(10)) // none of the above
`

#### Stored switcher

`typescript
const switcher = $switch(5)
.case(4, 'four')
.case(3, 'three')
.case(2, 'two')
.case(1, 'one')
.default('none of the above') // it does not run yet

console.log(switcher()) // none of the above
console.log(switcher.invoke()) // none of the above
console.log(switcher.invoke(1)) // none of the above
console.log(switcher(3)) // none of the above
`

#### more complex matching logic / runtime branch evaluation

`typescript
const switcher = $switch()
.case(
n => n % 2 === 0,
() => Math.floor(Math.random() * 10_000) + 1
)
.default(n => n ** n)

console.log(switcher(1)) // 1 (1^1)
console.log(switcher(2)) // random number between 1-10000
console.log(switcher(3)) // 27 (3^3)
console.log(switcher(4)) // random number between 1-10000
console.log(switcher(5)) // 3125 (5^5)
console.log(switcher(6)) // random number between 1-10000
console.log(switcher(7)) // 823543 (7^7)
``