Type utilities for Typescript and also Javascript
npm install @srhenry/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.

![Npm package version][npm]
![Npm package total downloads][npm]
![Npm package license][npm]
- 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
With NPM:
``bash`
npm install @srhenry/type-utils --save
With Yarn:
`bash`
yarn add @srhenry/type-utils
#### 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.foo
// if it has then check if it is string or undefined,`
// if it hasn't then pass anyway as it is optional property.
#### 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))
`
#### 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()
}));
`
#### 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 foofoo
} else {
// obj don't have a property of type string`
}
#### 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: '${obj.foo}')String is valid: '${str}'
.with(string().nonEmpty(), str => )
.default(() => { throw new TypeError('ðŸ˜') })
matcher.exec('foo') //String is valid: 'foo'
matcher.exec({ foo: 'bar' }) //Foo is valid: 'bar'
matcher.exec({ foo: 'ba' }) //TypeError: ðŸ˜
matcher.exec("") //TypeError: ðŸ˜
`
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
`
#### 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
declare const res2: Result
`
#### 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
declare const res2: AsyncResult
`
#### 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
`
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
`
---
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
`
---
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
new Promise
setTimeout(() => {
const id = uuid()
db['users'] ??= []
db['users']?.push({ id, ...user })
resolve(id)
}, 200)
})
const addPostFactory =
(db: Record
new Promise
setTimeout(() => {
db['posts'] ??= []
db['posts']?.push({ user_id, ...post })
resolve(true)
}, 300)
})
const db = {
users: [] as Record
posts: [] as Record
} as Record
const len =
const addPostCurried = (post: Record
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
`
---
> @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)
``