README

is-explicit

Why ?

You want to do explicit type checks.
You don't want to have to differentiate between typeof and instanceof
You keep a cool head and bring justice to chaos.

2.0

Breaking changes from the 1.x release, but the resulting changes make is-explicit faster and more composable.

Usage

npm install is-explicit

import is from 'is-explicit'

Does a variable have a value?

is.defined(undefined)         //false
is.defined(null)              //false
is.defined(NaN)               //false
is.defined(10)                //true

Is a variable a specific type?

is([], Object)         //true
is([], Array)          //true

is(true, Boolean)      //true
is(false, Boolean)     //true
is(10, Number)         //true

is('str', String)      //true
is('str', Object)      //false

is(new String('str'), String)   //true
is(new String('str'), Object)   //true

is(/expr/, RegExp)             //true
is(/expr/, Object)             //true

is(function(){}, Object)       //true
is(function(){}, Function)     //true

is(new function(){}, Object)   //true
is(new function(){}, Function) //False

is(Array, Object)      //true
is(Array, Function)    //true
is(Array, Array)       //false

is(Symbol(), Symbol)        //true
is(Symbol.iterator, Symbol) //true
is(Symbol(), Object)        //false

Is a variable a custom type?

function Foo() {}
is (new Foo(), Foo) // true

const foo = function(){}
const bar = function(){}

is(new foo(), foo) // true
is(new bar(), foo) // false

Is a variable one of multiple types?

is('str', [Number, Boolean, String]) // true

Types are expected to be functions:

is('str', 'otherstring') //throws Error

Is a value an Array of a specific type?

is.arrayOf(['str'], String)                       // == true
is.arrayOf([0, false, new Date(), 'str'], String) // == false
is.arrayOf([0,'str',10,'cake'], [String, Number]) // == true,

Is a value an Object of a specific type?

is.objectOf([ 0, 'str' ], String)                     // == false
is.objectOf({ }, String)                              // == false
is.objectOf({ foo: '1', bar: '2' }, String)           // == true
is.objectOf({ foo: '1', bar: 2 }, [ String, Number ]) // == true

Is a value a plain Object?

is.plainObject(['str'])             // == false
is.plainObject(new Date())          // == false
is.plainObject({})                  // == true
is.plainObject(new Object())        // == true

function FooBar() { }

is.plainObject(new FooBar)           // == false

Binding

Binding is now binds it to a type:

class Foo { }

const isFoo = Foo::is

isFoo(new Foo()) // true

Bind to multiple types:

const isBoolOrFunc = [ Boolean, Function ]::is

isBoolOrFunc(false) // true

Better composition:

const mixed = [ 0, 'string', 1, true, 2, Symbol('bad') ]

const numbers = mixed.filter(Number::is)

Shortcuts

import is from 'is-explicit'

const value = 'whatever'

is.string(value)    // == String::is(value)
is.number(value)    // == Number::is(value)
is.bool(value)      // == Boolean::is(value)
is.func(value)      // == Function::is(value)
is.symbol(value)    // == Symbol::is(value)
is.primitive(value) // == [ Boolean, Number, String ]::is(value)

is.arrayOf.string(value)    // == String::is.arrayOf
is.arrayOf.number (value)   // == Number::is.arrayOf
is.arrayOf.bool(value)      // == Boolean::is.arrayOf
is.arrayOf.symbol(value)    // == Symbol::is.arrayOf
is.arrayOf.func(value)      // == Function::is.arrayOf
is.arrayOf.primitive(value) // == [ Boolean, Number, String ]::is.arrayOf

is.objectOf.string(value)    // == String::is.objectOf
is.objectOf.number (value)   // == Number::is.objectOf
is.objectOf.bool(value)      // == Boolean::is.objectOf
is.objectOf.symbol(value)    // == Symbol::is.objectOf
is.objectOf.func(value)      // == Function::is.objectOf
is.objectOf.primitive(value) // == [ Boolean, Number, String ]::isArrayOf

Additional Helpers

import is from 'is-explicit'

is.defined() // returns true if input is not null, undefined or NaN

is.arrayOf.plainObject() // returns true if input is an array of plain objects

is.instanceable() // returns true if input is a function with a prototype (ie: arrow functions will return false)

is.subclassOf() // returns true if input is a class that extends the provided type

Usage no npm install needed!