ts-typecheck

A package for checking type in Javascript runtime environment.

Abstract

Typescript is awesome! I used in production on my Express node server. The thing is, data comes from my UI/Front End developers can be varied in types. Let say i would like a boolean, but my Front Ends can post a 'true' string instead, which could ruin my server.

That's why i created this package. I want to enable type check onto whatever they throw to my API server.

This checker is intellisense friendly, and will suggest the right type to whatever you need.

Usage Example

import typecheck from 'ts-typecheck'

function login(req, res) {
	const body = req.body

	if (typecheck(body, ['object', {
		username: 'string',
		password: 'string',
		type: ['enum?', ['default', 'social', 'sso']]
	}])) {
		...
		// This inner code will only run if req.body is an object with:
		// username as string, password as string, an optional enum type
	}

	// OR, you can do
	if (
		typecheck(body.username, 'string')
		&& typecheck(body.password, 'string')
		&& typecheck(body.type, ['enum?', ['default', 'social', 'sso']])
	) {
		...
	}
}

Supported Types

There are 3 type of types, Primitives, Custom, and Configurables. And on top of that, each of them support optional mark '?'. Optional mark will accept null and undefined type.

Primitives type are:

• bigint
• boolean
• function
• number
• string
• symbol
• undefined Practically, this is a shorthand for javascript typeof equality check. Usage:

typecheck(1, 'number') // Internaly, it would do `return typeof arguments[0] === 'number'`, returns true
typecheck('1', 'string') // The same, returns true
...

Custom type are:

• date Currently date is the only supported custom types. Internally it will check is the value a valid date object or js date int (e.g: value of Date.now()) or date string (e.g: 11/11/2011)

Configurables type are:

• object
• exact
• enum
• or
• array
• arrayshape These are the more advance use of typechecking. All Configurables types need to be supplied as an array of [type, configuration]. I know, this sounds complicated. Let me explain.

const user = {
	id: 1,
	name: 'Andree',
	roles: ['admin', 'user'],
	nationality: 'ID',
	phone: '+62 859 XXXX XXXX',
	metadata: {
		age: 21,
		log: ['ID', '12/12/2020 18:59', true]
	}
}

typecheck(user, ['object', {
	id: 'number',
	name: 'string',
	roles: ['array', ['enum', ['admin', 'user', 'superadmin']]]
	nationality: ['enum?', ['ID', 'AU', 'SG', 'US', 'UK']]
	phone: ['or?', ['string', 'number']]
	metadata: ['object?', {
		age: 'number?',
		log: ['arrayshape?', [['enum', ['ID', 'AU', 'SG', 'US', 'UK']], 'date', 'boolean']]
	}]
}])

// returns true

On the example above, the typecheck will return true. It will first check if user is an object that has id, name, roles, nationality (optional), phone (optional), and metadata (optional) as keys. Then it will proceed by checking if roles is an array of enum (one of: admin, user, or superadmin). The same goes for nationality. As for phone, it will check whether it satisfy either string or number. Next, it will check for metadata, and goes deeper to check the age and log keys. For log, it will check whether it is shaped as an array of [enum of nationality, date, boolean] or not. Using the same typecheck,

const user2 = {
	id: 2,
	name: 'John',
	roles: ['user'],
}

typecheck(user2, ...)
// returns true

const user3 = {
	id: 3,
	name: 'John',
	roles: ['user'],
	phone: 859123123123,
}

typecheck(user3, ...)
// also returns true

const user4 = {
	id: 4,
	name: 'Jane',
}

typecheck(user4, ...)
// returns false

const user5 = {
	id: 5,
	name: 'Jude',
	roles: ['user'],
	metadata: {}
}

typecheck(user5, ...)
// returns true

const user6 = {
	id: 6,
	name: 'Job',
	roles: ['user'],
	metadata: {
		log: ['ID']
	}
}

typecheck(user6, ...)
// returns false

object type

Check whether the value is an object that has at least the configured keys. If there are more keys than the configured one, the object will still pass the typecheck. For more strict object typecheck, please use exact.

const check: AllConfigurableTypes = ['object', {
	id: 'number',
	name: 'string',
}]

typecheck({
	id: 1,
	name: 'Andree'
	bio: 'Lorem ipsum...',
})
// returns true

exact type

Check whether the value is an object that has the same key as the configured keys.

const check: AllConfigurableTypes = ['exact', {
	id: 'number',
	name: 'string',
}]

typecheck({
	id: 1,
	name: 'Andree'
	bio: 'Lorem ipsum...',
})
// returns false

enum type

Check whether the supplied value satisfy any value of the supplied array.

typecheck('ID', ['enum', ['ID', 'AU', 'SG', 'US', 'UK']])
// returns true

typecheck('EN', ['enum', ['ID', 'AU', 'SG', 'US', 'UK']])
// returns false

or type

Check whether the supplied value satisfy any type of the supplied array. It's like enum for types.

typecheck('ID', ['or', ['string', 'number']])
// returns true

typecheck(1, ['or', ['string', 'number']])
// returns true

typecheck(true, ['or', ['string', 'number']])
// returns false

array type

Check whether the supplied value is an array.

typecheck(['ID'], ['array', 'string'])
// returns true

typecheck(['ID'], ['array', 'number'])
// returns false

typecheck(['ID'], ['array', ['enum', ['ID', 'AU', 'SG', 'US', 'UK']]])
// returns true

typecheck(['ID', 'ID', 'ID'], ['array', ['enum', ['ID', 'AU', 'SG', 'US', 'UK']]])
// returns true

typecheck(['ID', 'AU', 'UK', 'PH'], ['array', ['enum', ['ID', 'AU', 'SG', 'US', 'UK']]])
// returns false

typecheck([{
	id: 1,
	name: 'Andree',
}, {
	id: 2,
	name: 'John'
	nationality: 'ID',
}], ['array', ['object', {
	id: 'number',
	name: 'string',
	nationality: ['enum?', ['ID', 'AU', 'SG', 'US', 'UK']]
}]])
// returns true

arrayshape type

Check whether the supplied value has an exact shape of the configured array.

typecheck([1, 'Andree'], ['arrayshape', ['number', 'string']])
// returns true

typecheck([1, 'Andree'], ['arrayshape', ['number', 'string', 'boolean']])
// returns false

That's it folks! I am open to suggestion. Thanks for reading. Open ticket for any questions or bug. Helping hands are welcomed!