Typy

Type checking library for JavaScript with a 'sweeter' syntax.

t('foo').isString // => true

New in version 3 🔥

• Schema Validation
• Custom Types

Version 3.0.0 introduces BREAKING changes (for node.js CommonJS style imports only).

// Before v3.0.0, `t` function was imported as
const t = require('typy');
 
//From v3.0.0, `t` function should be imported as
const { t } = require('typy');
 
// Note: This version does not affect previous ES6 style imports._
import t, { Schema, addCustomTypes } from 'typy'; // this will still work
import { t, Schema, addCustomTypes } from 'typy'; // this will also work

Why?

There are a hundred other type checking libraries out there. But Typy is built with three core behavioral aspects.

1. No surprises. Typy will never throw, no matter what the input is.
2. Object check will only look for { } rather than JavaScript's native behavior of considering everything as objects such as arrays, functions, null, etc.
3. Thought Driven Development. Code should exactly mimic your thoughts on the logic rather than writing extra code just because that's how JavaScript works. t(obj).isDefined // => true
4. Custom type validation and schema validation.

Install

$ npm install --save typy

Usage

import t from 'typy'; // ES6 style import
// var t = require('typy'); // CommonJS style import (version < 3)
// var t = require('typy').default; // CommonJS style import (version >= 3)
 
if (t('hello').isString) { // => true
  console.log('Input is a String!')
} else {
  console.log('Input is not a String!')
}
 
// More examples
t('22').isNumber // => false
t('22').isString // => true
t({}).isObject // => true
t([]).isArray // => true
t([]).isObject // => false
 
const sym = Symbol('typyIsAwesome');
t(sym).isSymbol // => true
 
// obj.goodKey.nestedKey = 'helloworld'
t(obj, 'goodKey.nestedKey').isDefined // => true
t(obj, 'badKey.nestedKey').isDefined // => false
// Typy won't throw undefined error for badKey.nestedKey
 
// to check if obj.goodKey.nestedKey is a string
t(obj, 'goodKey.nestedKey').isString // => true
t(obj, 'badKey.nestedKey').isString // => false
 
const deepObj = {
  nestedKey: {
    goodKey: 'hello',
    superNestedKey: {}
  }
};
// safely return the value from a nested key in an object
const myObj = t(deepObj, 'nestedKey.goodKey').safeObject; // => 'hello'
// Typy won't throw undefined error for badKey.goodKey
// instead the return value will be undefined
const myObj = t(deepObj, 'badKey.goodKey').safeObject; // => undefined

API

• t(input, optionalObjectPath)
• isDefined
• isUndefined
• isNull
• isNullOrUndefined
• isBoolean
• isTrue
• isFalse
• isTruthy
• isFalsy
• isObject
• isEmptyObject
• isString
• isEmptyString
• isNumber
• isArray
• isEmptyArray
• isFunction
• isDate
• isSymbol
• safeObject
• safeObjectOrEmpty
• safeString
• safeNumber
• safeBoolean
• safeFunction
• safeArray
• isValid (Schema Validation)
• addCustomTypes (Custom Types)

t(input, optionalObjectPath)

Pass in your input to the t() method and Typy will take care of everything

// you can pass any type of input
// Number, String, Object, null, undefined, Array, anything
t('str')
t(22)
t({foo: 'fooooo', bar: 'barooo'})
t([2, 'three', 'hey'])
 
const obj = {
  goodKey: {
    nestedKey: 'hello world'
  }
}
// To pass nested path of an object
// Ex. obj.goodKey.nestedKey
// You have to pass the path as string in the second param
t(obj, 'goodKey.nestedKey')
t(obj, 'badKey.nestedKey')
// this is because if you pass t(obj.badKey.nestedKey),
// you will get undefined exception
// because that is how javascript is designed
// to overcome that we need to pass the sub key as a string to Typy

isDefined

Returns true if the input is defined.

const obj = {
  goodKey: 'hello'
}
 
t(obj.goodKey).isDefined // => true
t(obj.badKey).isDefined // => false

isUndefined

Returns true if the input is undefined.

const obj = {
  goodKey: 'hello'
}
 
t(obj.goodKey).isUndefined // => false
t(obj.badKey).isUndefined // => true

isNull

Returns true if the input is null.

const obj = {
  foo: null
}
 
t(obj.foo).isNull // => true

isNullOrUndefined

Returns true if the input is null or undefined.

const obj = {
  foo: null
}
 
t(obj.foo).isNullOrUndefined // => true
t(obj.bar).isNullOrUndefined // => true

isBoolean

Returns true if the input is either true or false.

t(true).isBoolean // => true
t(false).isBoolean // => true

isTrue

Returns true if the input is Boolean true.

t(true).isTrue // => true
t(false).isTrue // => false

isFalse

Returns true if the input is Boolean false.

t(true).isFalse // => false
t(false).isFalse // => true

isTruthy

Returns true if the input is considered truthy.

In JavaScript anything other than false, 0, '', "", null, undefined and NaN is considered truthy.

t('Typy is amazing =)').isTruthy // => true
t({}).isTruthy // => true
t(22).isTruthy // => true
t([1, 'two']).isTruthy // => true

isFalsy

Returns true if the input is considered falsy.

In JavaScript any of these values false, 0, '', "", null, undefined and NaN are considered falsy.

t(0).isFalsy // => true
t(null).isFalsy // => true
t(undefined).isFalsy // => true
t(false).isFalsy // => true

isObject

Returns true if the input is an object.

const obj = {
  foo: null
}
 
t(obj).isObject // => true
t({}).isObject // => true

Note: Only { } objects will return this as true as opposed to javascript definition of Object which includes Arrays, Functions, anything and everything related to prototype. This is an intentional behavior as we don't want arrays to return true for isObject.

isEmptyObject

Returns true if the input is an empty object, aka object without any keys.

const obj = {
  foo: 'hello there',
  bar: {}
}
 
t(obj.bar).isEmptyObject // => true
t({}).isEmptyObject // => true
t(obj).isEmptyObject // => false

isString

Returns true if the input is a string.

const obj = {
  foo: 'typy is awesome =)',
}
t(obj.foo).isString // => true
t('').isString // => true
t(22).isString // => false
t(null).isString // => false

isEmptyString

Returns true if the input is an empty string.

t('').isEmptyString // => true
t('typy is so great').isEmptyString // => false

isNumber

Returns true if the input is a number.

t(22).isNumber // => true
t('i am a string').isNumber // => false
t({}).isNumber // => false

isArray

Returns true if the input is an array.

t([]).isArray // => true
t([1, 2, 'typy']).isArray // => true
t({}).isArray // => false

isEmptyArray

Returns true if the input is an empty array.

t([]).isEmptyArray // => true
t([1, 2, 'typy']).isEmptyArray // => false

isFunction

Returns true if the input is a function.

const func = () => {};
t(func).isFunction // => true
t({}).isFunction // => false

isDate

Returns true if the input is a javascript's date object.

const date = new Date();
t(date).isDate // => true
t({}).isDate // => false

isSymbol

Returns true if the input is a javascript's Symbol.

const mySym = Symbol(123);
const anotherSymbol = Symbol('typyIsAwesome');
 
t(mySym).isSymbol // => true;
t(Object(anotherSymbol)).isSymbol  // => true;
 
t({}).isSymbol // => false
t([]).isSymbol // => false
t(null).isSymbol // => false

safeObject

Safely returns the value from a nested object path without throwing any error.

const deepObj = {
  nestedKey: {
    goodKey: 'hello',
    superNestedKey: {}
  }
};
// Typy can safely return the value from a nested key in an object
const myObj = t(deepObj, 'nestedKey.goodKey').safeObject; // => 'hello'
// Typy won't throw if the key at any level is not found
// instead will return undefined
const myObj = t(deepObj, 'badKey.goodKey').safeObject; // => undefined
 
const anotherDeepObj = {
  nestedArray: [{
    goodKey: 'hello one',
    superNestedKey: {}
  }, {
    goodKey: 'hello two',
    superNestedKey: {
      superGoodKey: 'typy is great :)'
    }
  }]
};
// Typy can safely return the value even from a nested key in a nested array
const myObj = t(anotherDeepObj, 'nestedArray[1].superNestedKey.superGoodKey').safeObject; // => 'typy is great :)'

safeObjectOrEmpty

Safely returns the value from a nested object path if the path exists or returns an empty object if the.

const deepObj = {
  nestedKey: {
    goodKey: 'hello',
    superNestedKey: {}
  }
};
// Typy can safely return the value from a nested key in an object
const myObj = t(deepObj, 'nestedKey.goodKey').safeObjectOrEmpty; // => 'hello'
// Typy won't throw if the key at any level is not found
// instead will return an empty object
const myObj = t(deepObj, 'badKey.goodKey').safeObjectOrEmpty; // => {}
 
const anotherDeepObj = {
  nestedArray: [{
    goodKey: 'hello one',
    superNestedKey: {}
  }, {
    goodKey: 'hello two',
    superNestedKey: {
      superGoodKey: 'typy is great :)'
    }
  }]
};
// Typy can safely return the value even from a nested key in a nested array
const myObj = t(anotherDeepObj, 'nestedArray[1].superNestedKey.superGoodKey').safeObjectOrEmpty; // => 'typy is great :)'

safeString

Returns the string value if the input type is string or will return an empty string ''.

const str = t('typy is safe').safeString; // => 'typy is safe'
const str = t(null).safeString; // => ''
const str = t(undefined).safeString; // => ''
const str = t(22).safeString; // => ''

safeNumber

Returns the number if the input type is Number or will return 0.

const num = t(22).safeNumber; // => 22
const num = t('22').safeNumber; // => 0
const num = t(undefined).safeNumber; // => 0
const num = t(null).safeNumber; // => 0

safeBoolean

Returns the boolean if the input type is Boolean or will return false.

const bool = t(true).safeBoolean; // => true
const bool = t(false).safeBoolean; // => false
const bool = t('22').safeBoolean; // => false
const bool = t(undefined).safeBoolean; // => false
const bool = t(22).safeBoolean; // => false

safeFunction

Returns the function if the input type is function or will return an empty function () => {}.

const helloFunc = () => { return 'Hello World!' }
const func = t(helloFunc).safeFunction; // => helloFunc reference
const func = t('I am a string').safeFunction; // => empty function () => {}
const func = t(undefined).safeFunction; // => empty function () => {}
const func = t(null).safeFunction; // => empty function () => {}

safeArray

Safely returns the value from a nested object path or an empty array. If the path specified exists but is not an array, returns an array containing the value of the specified path.

const deepObj = {
  nestedKey: [
    {
      goodKey: ['hello'],
      numberKey: 10,
      superNestedKey: {}
    },
  ]
};
// Typy can safely return the value from a nested key in an object or an array
const myObj = t(deepObj, 'nestedKey').safeArray; // => [ { goodKey: ['hello'], numberKey: 10, superNestedKey: {} } ]
const myObj = t(deepObj, 'nestedKey[0].goodKey').safeArray; // => ['hello']
// Typy can wrap a value or object inside an array
const myObj = t(deepObj, 'nestedKey[0].numberKey').safeArray; // => [ 10 ]
const myObj = t(deepObj, 'nestedKey[0].superNestedKey').safeArray; // => [ {} ]
// Typy won't throw if the key at any level is not found
// instead will return an empty array
const myObj = t(deepObj, 'nestedKey[1]').safeArray; // => []
const myObj = t(deepObj, 'badKey.goodKey').safeArray; // => []

isValid (Schema Validation)

isValid is used to check and validate the schema of an object. It returns true if the schema of the object matches the schema passed or false if the schema doesn't match.

import t, { Schema } from 'typy';
 
const superheroSchema = {
  name: Schema.String,
  age: Schema.Number,
  appearances: [
    {
      title: Schema.String,
      alias: Schema.String,
    }
  ],
  lastSeen: Schema.Date
};
const batmanObject = {
  name: 'Batman',
  age: 45,
  isAlive: true,
  appearances: [
    {
      title: 'The Dark Knight',
      alias: 'Bruce',
    }
  ],
  lastSeen: new Date(14894561568)
};
const isSchemaValid = t(batmanObject, superheroSchema).isValid; // true
 
const simpleSchema = {
  name: Schema.String,
  arr: Schema.Array
};
const obj = {
  name: 'Jack',
  arr: [1, 2, 3]
};
const isSchemaValid = t(obj, simpleSchema).isValid; // true

The following Schema types are available in typy.

• Number
• String
• Array
• Boolean
• Null
• Undefined
• Function
• Date

addCustomTypes (Custom Types)

addCustomTypes is used to pass custom validators to Typy. It can be used to validate any ipnut for custom types, like this t(input).isMyCustomType.

You will have to add custom types only once in the project (preferabby in entry file. ex. index.js)

Entry file (Ex. index.js)

import t, { addCustomTypes } from 'typy';
 
addCustomTypes({
  isPhone: (input) => (t(input).isNumber && /^\d{10}$/g.test(String(input))), // has 10 digits
  isAddress: (input) => (t(input).isString && input.toUpperCase().includes('STREET')) // includes 'street' in input
});
 

Anywhere in the project

import t from 'typy';
 
const isThePhoneNumberValid = t(9892389239).isPhone; // => true
const isThePhoneNumberValid = t('abcdefg').isPhone; // => false
 
const isTheAddressValid = t('10 Downing Street').isAddress; // => true
const isTheAddressValid = t('I like cats 🐈').isAddress; // => false
 

Contributors

Thanks goes to these amazing people 🎉

Dinesh Pandiyan	Ozair Patel	Aneerudh	Ruphaa Ganesh	Quentin Jadeau	dan
Robert Schadek	Michael Kirkpatrick	Ana Liza Pandac	Abdul Rehman

License

MIT © Dinesh Pandiyan