go-types
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Type-checking utilities for JavaScript
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# Go Types
**Type-checking utilities for JavaScript.**
[](https://github.com/koyote130708/go-types#documentation)
[](https://www.paypal.com/donate/?business=T7Q29NNMZVW98\&no_recurring=0\&item_name=Your+support+will+help+us++continue+our+work+and+improve+the+quality+of+our+products.+Thank+you!\¤cy_code=USD)
* **version**: 1.3.1
* **license**: MIT
<br />
## Installation
```javascript
npm i go-types
```
or
```javascript
yarn add go-types
```
<br />
## Usage
### ES6
```javascript
import Types from 'go-types'
Types.isArray([]);
```
or
```javascript
import { isArray } from 'go-types';
isArray([]);
```
### Node
```javascript
const Types = require('go-types');
Types.isArray([]);
```
or
```javascript
const { isArray } = require('go-types');
isArray([]);
```
### Web browser
```javascript
<script src="dist/go-types.min.js"></script>
<script>
const { isArray } = Types;
isArray([]);
</script>
```
<br />
## Documentation
<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
#### Table of Contents
* [Primitive](#primitive)
* [isUndefined](#isundefined)
* [Parameters](#parameters)
* [Examples](#examples)
* [isNull](#isnull)
* [Parameters](#parameters-1)
* [Examples](#examples-1)
* [isBoolean](#isboolean)
* [Parameters](#parameters-2)
* [Examples](#examples-2)
* [isNumber](#isnumber)
* [Parameters](#parameters-3)
* [Examples](#examples-3)
* [isString](#isstring)
* [Parameters](#parameters-4)
* [Examples](#examples-4)
* [isSymbol](#issymbol)
* [Parameters](#parameters-5)
* [Examples](#examples-5)
* [isBigInt](#isbigint)
* [Parameters](#parameters-6)
* [Examples](#examples-6)
* [isPrimitive](#isprimitive)
* [Parameters](#parameters-7)
* [Examples](#examples-7)
* [Utility](#utility)
* [isNullish](#isnullish)
* [Parameters](#parameters-8)
* [Examples](#examples-8)
* [isEmpty](#isempty)
* [Parameters](#parameters-9)
* [Examples](#examples-9)
* [isBlank](#isblank)
* [Parameters](#parameters-10)
* [Examples](#examples-10)
* [isTruthy](#istruthy)
* [Parameters](#parameters-11)
* [Examples](#examples-11)
* [isFalsy](#isfalsy)
* [Parameters](#parameters-12)
* [Examples](#examples-12)
* [isTypeOf](#istypeof)
* [Parameters](#parameters-13)
* [Examples](#examples-13)
* [Number](#number)
* [isInteger](#isinteger)
* [Parameters](#parameters-14)
* [Examples](#examples-14)
* [isFloat](#isfloat)
* [Parameters](#parameters-15)
* [Examples](#examples-15)
* [isFinite](#isfinite)
* [Parameters](#parameters-16)
* [Examples](#examples-16)
* [isInfinite](#isinfinite)
* [Parameters](#parameters-17)
* [Examples](#examples-17)
* [isNaN](#isnan)
* [Parameters](#parameters-18)
* [Examples](#examples-18)
* [isNumeric](#isnumeric)
* [Parameters](#parameters-19)
* [Examples](#examples-19)
* [Object](#object)
* [isObject](#isobject)
* [Parameters](#parameters-20)
* [Examples](#examples-20)
* [isPlainObject](#isplainobject)
* [Parameters](#parameters-21)
* [Examples](#examples-21)
* [isCyclic](#iscyclic)
* [Parameters](#parameters-22)
* [Examples](#examples-22)
* [isIterable](#isiterable)
* [Parameters](#parameters-23)
* [Examples](#examples-23)
* [isFunction](#isfunction)
* [Parameters](#parameters-24)
* [Examples](#examples-24)
* [isDate](#isdate)
* [Parameters](#parameters-25)
* [Examples](#examples-25)
* [isValidDate](#isvaliddate)
* [Parameters](#parameters-26)
* [Examples](#examples-26)
* [isInvalidDate](#isinvaliddate)
* [Parameters](#parameters-27)
* [Examples](#examples-27)
* [isRegExp](#isregexp)
* [Parameters](#parameters-28)
* [Examples](#examples-28)
* [isPromise](#ispromise)
* [Parameters](#parameters-29)
* [Examples](#examples-29)
* [isPromiseLike](#ispromiselike)
* [Parameters](#parameters-30)
* [Examples](#examples-30)
* [isThenable](#isthenable)
* [Parameters](#parameters-31)
* [Examples](#examples-31)
* [isError](#iserror)
* [Parameters](#parameters-32)
* [Examples](#examples-32)
* [Array](#array)
* [isArray](#isarray)
* [Parameters](#parameters-33)
* [Examples](#examples-33)
* [isArrayOf](#isarrayof)
* [Parameters](#parameters-34)
* [Examples](#examples-34)
* [isArrayLike](#isarraylike)
* [Parameters](#parameters-35)
* [Examples](#examples-35)
* [isArrayLikeOf](#isarraylikeof)
* [Parameters](#parameters-36)
* [Examples](#examples-36)
* [isPair](#ispair)
* [Parameters](#parameters-37)
* [Examples](#examples-37)
* [Collection](#collection)
* [isMap](#ismap)
* [Parameters](#parameters-38)
* [Examples](#examples-38)
* [isSet](#isset)
* [Parameters](#parameters-39)
* [Examples](#examples-39)
* [isWeakMap](#isweakmap)
* [Parameters](#parameters-40)
* [Examples](#examples-40)
* [isWeakSet](#isweakset)
* [Parameters](#parameters-41)
* [Examples](#examples-41)
* [Node](#node)
* [isNode](#isnode)
* [Parameters](#parameters-42)
* [Examples](#examples-42)
* [isElement](#iselement)
* [Parameters](#parameters-43)
* [Examples](#examples-43)
* [isFragment](#isfragment)
* [Parameters](#parameters-44)
* [Examples](#examples-44)
### Primitive
#### isUndefined
Determines whether the value is <code>undefined</code>.
##### Parameters
* `value` **any** The value to check.
##### Examples
Undefined values
```javascript
// returns true
isUndefined(undefined);
isUndefined(void 0);
```
Non-undefined values
```javascript
// returns false
isUndefined(null);
isUndefined(false);
isUndefined(0);
isUndefined("");
isUndefined(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is <code>undefined</code>; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isNull
Determines whether the value is <code>null</code>.
##### Parameters
* `value` **any** The value to check.
##### Examples
Null values
```javascript
// returns true
isNull(null);
```
Non-null values
```javascript
// returns false
isNull(undefined);
isNull(false);
isNull(0);
isNull("");
isNull(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is <code>null</code>; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isBoolean
* **See**: Types.isPrimitive
* **See**: Types.isObject
* **See**: Types.isTypeOf
Determines whether the value is a primitive boolean or <code>Boolean</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Boolean values
```javascript
// returns true
isBoolean(true);
isBoolean(new Boolean(true));
```
Non-boolean values
```javascript
// returns false
isBoolean(1);
isBoolean("true");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a primitive boolean or <code>Boolean</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isNumber
* **See**: Types.isPrimitive
* **See**: Types.isObject
* **See**: Types.isTypeOf
Determines whether the value is a primitive number or <code>Number</code> object
which includes the "special" numbers `+Infinity`, `-Infinity` and `NaN`.
##### Parameters
* `value` **any** The value to check.
##### Examples
Number values
```javascript
// returns true
isNumber(1);
isNumber(-12.34);
isNumber(new Number(1));
isNumber(Infinity);
isNumber(NaN);
```
Non-number values
```javascript
// returns false
isNumber("1");
isNumber(true);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a primitive number or <code>Number</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isString
* **See**: Types.isPrimitive
* **See**: Types.isObject
* **See**: Types.isTypeOf
Determines whether the value is a primitive string or <code>String</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
String values
```javascript
// returns true
isString("1");
isString(new String("abc"));
```
Non-string values
```javascript
// returns false
isString(1);
isString(["a", "b"]);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a primitive string or <code>String</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isSymbol
* **See**: Symbol
Determines whether the value is a primitive <code>Symbol</code>.
##### Parameters
* `value` **any** The value to check.
##### Examples
Symbol values
```javascript
// returns true
isSymbol(Symbol("abc"));
```
Non-Symbol values
```javascript
// returns false
isSymbol("abc");
isSymbol(/[a-z]/);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a primitive <code>Symbol</code>; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isBigInt
* **See**: BigInt
Determines whether the value is a primitive <code>BigInt</code>.
##### Parameters
* `value` **any** The value to check.
##### Examples
BigInt values
```javascript
// returns true
isBigInt(BigInt(1));
isBigInt(BigInt(-1234567890));
```
Non-BigInt values
```javascript
// returns false
isBigInt(Number.MAX_VALUE);
isBigInt(Infinity);
isBigInt(NaN);
isBigInt("1n");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a primitive <code>BigInt</code>; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isPrimitive
Determines whether the value is a primitive value.
##### Parameters
* `value` **any** The value to check.
##### Examples
Primitive values
```javascript
// returns true
isPrimitive(undefined);
isPrimitive(null);
isPrimitive(false);
isPrimitive(0);
isPrimitive("abc");
isPrimitive(Symbol("abc"));
isPrimitive(BigInt(1234567890));
```
Non-primitive values
```javascript
// returns false
isPrimitive(new Number(1));
isPrimitive([1, 2, 3]);
isPrimitive(function () {});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a primitive value; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
### Utility
#### isNullish
* **See**: undefined
* **See**: null
Determines whether the value is <code>null</code> or <code>undefined</code>.
##### Parameters
* `value` **any** The value to check.
##### Examples
Nullish values
```javascript
// returns true
isNullish();
isNullish(undefined);
isNullish(void 0);
```
Non-nullish values
```javascript
// returns false
isNullish(null);
isNullish(false);
isNullish(0);
isNullish("");
isNullish([]);
isNullish(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is <code>null</code> or <code>undefined</code>; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isEmpty
Determines whether the value is an empty value which can be one of the following:
* <code>null</code>
* <code>undefined</code>
* A string whose length is zero
* An array with no elements
* A plain object with no enumerable keys
* An iterable with no iterable values
##### Parameters
* `value` **any** The value to check.
##### Examples
Empty values
```javascript
// returns true
isEmpty(null);
isEmpty(undefined);
isEmpty("");
isEmpty([]);
isEmpty({});
isEmpty(new Set());
```
Non-empty values
```javascript
// returns false
isEmpty(" ");
isEmpty(0);
isEmpty(false);
isEmpty([null]);
isEmpty({a: ""});
isEmpty(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an empty value; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isBlank
Determines whether the value is a blank value which can be one of the following:
* <code>null</code>
* <code>undefined</code>
* A string whose length is zero or has only space characters
* An array that has no elements or has only nullish values
* A plain object that has no enumerable keys or has only nullish values
* An iterable that has no iterable values or has only nullish values.
##### Parameters
* `value` **any** The value to check.
##### Examples
Blank values
```javascript
// returns true
isBlank(null);
isBlank(undefined);
isBlank(" \t\n ");
isBlank([undefined, null]);
isBlank({a: null, b: undefined});
isBlank(new Set(null));
```
Non-blank values
```javascript
// returns false
isBlank(0);
isBlank(false);
isBlank(" a ");
isBlank([""]);
isBlank({a: ""});
isBlank(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a blank value; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isTruthy
Determines whether the value is a truthy value.
A truthy value is a value that is considered true when encountered in a Boolean context.
All values are truthy except <code>false</code>, <code>0</code>, <code>""</code>, <code>undefined</code>, <code>null</code> and <code>NaN</code>.
##### Parameters
* `value` **any** The value to check.
##### Examples
Truthy values
```javascript
// returns true
isTruthy(true);
isTruthy(1);
isTruthy("false");
isTruthy(new Boolean(false));
isTruthy({});
```
Non-truthy values
```javascript
// returns false
isTruthy(false);
isTruthy(0);
isTruthy("");
isTruthy(undefined);
isTruthy(null);
isTruthy(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a truthy value; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isFalsy
Determines whether the value is a falsy value which can be one of the following:
* <code>false</code>
* <code>0</code>
* <code>""</code>
* <code>undefined</code>
* <code>null</code>
* <code>NaN</code>
##### Parameters
* `value` **any** The value to check.
##### Examples
Falsy values
```javascript
// returns true
isFalsy(false);
isFalsy(0);
isFalsy("");
isFalsy(undefined);
isFalsy(null);
isFalsy(NaN);
```
Non-falsy values
```javascript
// returns false
isFalsy(true);
isFalsy(-1);
isFalsy("false");
isFalsy(new Boolean(false));
isFalsy({});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a falsy value; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isTypeOf
Determines whether the value has a specified type.
Based on the type of the type value, it will check the following:
* string - checks if the type matches (case-sensitive) using the <code>typeof</code> operator.
* function - checks if the value is an instance of the function/class using the <code>instanceof</code> operator; if the test returns <code>false</code>, it checks if the function returns a truthy value when invoked with the value.
* null/undefined - checks if the value is equal to the type using the strict equality (<code>===</code>) operator.
* array - checks if the value has any type defined in the array.
##### Parameters
* `value` **any** The value to check.
* `type` **([string](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) | [Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function) | null | [undefined](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/undefined) | [Array](#array))** The expected type
##### Examples
Matching type values
```javascript
// returns true
isTypeOf(1, "number");
isTypeOf({a: 1}, Object);
isTypeOf("abc", ["string", undefined]);
```
Non-matching type values
```javascript
// returns false
isTypeOf(1, "boolean");
isTypeOf("", String);
isTypeOf(null, ["string", String]);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is of the type; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
### Number
#### isInteger
Determines whether the value is an integer (a primitive number or <code>Number</code> object).
##### Parameters
* `value` **any** The value to check.
##### Examples
Integer values
```javascript
// returns true
isInteger(1);
isInteger(new Number(1));
```
Non-integer values
```javascript
// returns false
isInteger(isInteger(0.1));
isInteger("1");
isInteger(Infinity);
isInteger(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an integer; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isFloat
Determines whether the value is a finite number with a decimal point (a primitive number or <code>Number</code> object).
##### Parameters
* `value` **any** The value to check.
##### Examples
Float values
```javascript
// returns true
isFloat(0.1);
isFloat(-1234.56789);
isFloat(new Number(0.1));
```
Non-float values
```javascript
// returns false
isFloat(1);
isFloat(1.0);
isFloat("1.2");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a finite number with a decimal point; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isFinite
* **See**: isFinite
Determines whether the value is a finite number (a primitive number or <code>Number</code> object).
##### Parameters
* `value` **any** The value to check.
##### Examples
Finite values
```javascript
// returns true
isFinite(0);
isFinite(-0.1);
isFinite(Number.MAX_VALUE);
```
Non-finite values
```javascript
// returns false
isFinite(Infinity);
isFinite("1");
isFinite(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a finite number; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isInfinite
* **See**: isFinite
Determines whether the value is a primitive number or <code>Number</code> object that represents positive or negative infinity.
##### Parameters
* `value` **any** The value to check.
##### Examples
Infinite values
```javascript
// returns true
isInfinite(Infinity);
isInfinite(Number.NEGATIVE_INFINITY);
```
Non-infinite values
```javascript
// returns false
isInfinite(Number.MAX_VALUE);
isInfinite(NaN);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a number that represents positive or negative infinity; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isNaN
* **See**: Number.isNaN
Determines whether the value is <code>NaN</code> (a primitive number or a <code>Number</code> object).
NaN is the only value in javascript that is not equal to itself.
##### Parameters
* `value` **any** The value to check.
##### Examples
NaN values
```javascript
// returns true
isNaN(NaN);
isNaN(new Number(NaN));
isNaN(0/0);
```
Non-NaN values
```javascript
// returns false
isNaN(undefined);
isNaN(null);
isNaN("NaN");
isNaN(Infinity);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is <code>NaN</code>; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isNumeric
Determines whether the value is a numeric value which can be one of the following:
* A primitive number or <code>Number</code> object that has a finite value
* A primitive string or <code>String</code> object that represents a finite number
* A BigInt
##### Parameters
* `value` **any** The value to check.
##### Examples
Numeric values
```javascript
// returns true
isNumeric(1);
isNumeric(new Number(1));
isNumeric("1.0");
isNumeric(new String("-1.234e+8"))
isNumeric(BigInt(1234567890));
isNumeric(Infinity);
```
Non-numeric values
```javascript
// returns false
isNumeric(NaN);
isNumeric(Infinity);
isNumeric("12000n");
isNumeric("1*2");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a numeric value; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
### Object
#### isObject
Determines whether the value is an <code>Object</code>.
##### Parameters
* `value` **any** The value to check.
##### Examples
Object values
```javascript
// returns true
isObject({a: 1, b: 2});
isObject(["a", "b"]);
isObject(new Object());
isObject(new Number(1));
isObject(function() {});
```
Non-object values
```javascript
// returns false
isObject(null);
isObject("abc");
isObject(Symbol("abc"));
isObject(1);
isObject(BigInt(1));
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an <code>Object</code>; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isPlainObject
Determines whether the value is a plain object created using object literal or by the <code>Object</code> constructor.
##### Parameters
* `value` **any** The value to check.
##### Examples
Plain object values
```javascript
// returns true
isPlainObject({a: 1, b: 2});
isPlainObject(new Object());
```
Non-plain-object values
```javascript
// returns false
isPlainObject(null);
isPlainObject("abc");
isPlainObject([1, 2]);
isPlainObject(new Number(1));
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a plain object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isCyclic
Determines whether the value is an cyclic object with a circular reference.
A cycle object has an enumerable property (or a sub-property) whose value points
to the object itself or a property of the object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Cyclic object
```javascript
// returns true
var obj = {};
obj.ref = obj;
isCyclic(obj);
```
Non-cyclic values
```javascript
// returns false
isCyclic({a: 1, b: 2});
isCyclic([1, 2, 3]);
isCyclic("abc");
isCyclic(function() {});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a cyclic object with a circular reference; <code>false</code> otherwise.
**Meta**
* **since**: 1.2.0
#### isIterable
* **See**: Iterable
Determines whether the value is iterable which can be used in a <code>for..of</code> operator.
##### Parameters
* `value` **any** The value to check.
##### Examples
Iterable values
```javascript
// returns true
isIterable([1, 2, 3]);
isIterable("abc");
isIterable(new Map());
isIterable(new Set());
isIterable({[Symbol.iterator]: function() {}});
```
Non-iterable values
```javascript
// returns false
isIterable({a: 1, b: 2});
isIterable(12345);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is iterable; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isFunction
Determines whether the value is a <code>Function</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Function values
```javascript
// returns true
isFunction(function() {});
isFunction(Object);
```
Non-function values
```javascript
// returns false
isFunction(null);
isFunction(new Object());
isFunction("function() {}");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>Function</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isDate
* **See**: Date
Determines whether the value is a <code>Date</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Date values
```javascript
// returns true
isDate(new Date());
isDate(new Date(""));
```
Non-date values
```javascript
// returns false
isDate("2001-01-01T00:00:00.000Z");
isDate(978307200000);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>Date</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isValidDate
* **See**: Date
Determines whether the value is a valid <code>Date</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Valid Date objects
```javascript
// returns true
isValidDate(new Date());
isValidDate(new Date("2001-01-01T00:00:00.000Z"));
isValidDate(new Date(-1));
```
Invalid Date & non-date values
```javascript
// returns false
isValidDate(new Date(""));
isValidDate("2001-01-01T00:00:00.000Z");
isValidDate(978307200000);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a valid <code>Date</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.3.0
#### isInvalidDate
* **See**: Date
Determines whether the value is an invalid <code>Date</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Invalid Date objects
```javascript
// returns true
isInvalidDate(new Date(""));
isInvalidDate(new Date(NaN));
```
Valid Date & non-date values
```javascript
// returns false
isInvalidDate(new Date());
isInvalidDate("2001-01-01T00:00:00.000Z");
isInvalidDate(978307200000);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an invalid <code>Date</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.3.0
#### isRegExp
* **See**: RegExp
Determines whether the value is a <code>RegExp</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
RegExp values
```javascript
// returns true
isRegExp(/[a-z]/);
isRegExp(new RegExp("[a-z]"));
```
Non-RegExp values
```javascript
// returns false
isRegExp("[a-z]");
isRegExp("/[a-z]/");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>RegExp</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isPromise
* **See**: Promise
Determines whether the value is a <code>Promise</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Promise values
```javascript
// returns true
isPromise(new Promise(resolve, reject));
isPromise(Promise.resolve());
isPromise(Promise.reject());
```
Non-promise values
```javascript
// returns false
isPromise({then: function() {}, catch: function() {}});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>Promise</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isPromiseLike
* **See**: [Promise API Reference](https://www.promisejs.org/api)
Determines whether the value is an object that defines <code>then</code> and <code>catch</code> methods.
##### Parameters
* `value` **any** The value to check.
##### Examples
Promise-like objects
```javascript
// returns true
isPromiseLike(new Promise(resolve, reject));
isPromiseLike({then: function() {}, catch: function() {}});
```
Non-promise-like values
```javascript
// returns false
isPromiseLike({then: function() {}});
isPromiseLike({then: true, catch: true});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a Promise-like object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isThenable
Determines whether the value is an object that defines a <code>then</code> method.
##### Parameters
* `value` **any** The value to check.
##### Examples
Thenable objects
```javascript
// returns true
isThenable(new Promise(resolve, reject));
isThenable({then: function() {}});
```
Non-thenable values
```javascript
// returns false
isThenable(null);
isThenable({then: true});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a thenable object; <code>false</code> otherwise.
**Meta**
* **since**: 1.1.0
#### isError
* **See**: Error
Determines whether the value is an <code>Error</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Error objects
```javascript
// returns true
isError(new Error("Validation error"));
isError(new TypeError("Expected a number, but found: " + value));
```
Non-Error values
```javascript
// returns false
isError(null);
isError(NaN);
isError(Promise.reject());
isError({name: "TypeError", message: "Expected a number"});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an <code>Error</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
### Array
#### isArray
Determines whether the value is an <code>Array</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Array values
```javascript
// returns true
isArray(["a", "b"]);
isArray(new Array());
```
Non-array values
```javascript
// returns false
isArray("abc");
isArray({length: 0});
isArray(new Int8Array());
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an <code>Array</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isArrayOf
Determines whether the value is a non-empty array and all elements in the array have the specified type.
##### Parameters
* `value` **any** The value to check.
* `type` **([string](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) | [Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function) | null | [undefined](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/undefined) | [Array](#array))** The type of elements
##### Examples
Matching values
```javascript
// returns true
isArrayOf([1, 2, 3], "number");
isArrayOf(["a", "b", null], ["string", null]);
isArrayOf([{a: 1}, {b: 2}], Object);
```
Non-matching values
```javascript
// returns false
isArrayOf([1, 2, "c"], "number");
isArrayOf([], undefined);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a non-empty array and and all elements in the array have the specified type; <code>false</code> otherwise.
**Meta**
* **since**: 1.1.0
#### isArrayLike
Determines whether the value is an array-like object with a "length" property
whose value is an integer and is within 0 ~ Number.MAX\_SAFE\_INTEGER (both inclusive).
##### Parameters
* `value` **any** The value to check.
##### Examples
Array-like objects
```javascript
// returns true
isArrayLike([]);
isArrayLike("abc");
isArrayLike({length: 0});
isArrayLike(new Int8Array());
```
Non-array-like values
```javascript
// returns false
isArrayLike({});
isArrayLike({length: -1})
isArrayLike(new Set());
isArrayLike(Array);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an array-like object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isArrayLikeOf
Determines whether the value is a non-empty array-like object and all elements in the object have the specified type.
##### Parameters
* `value` **any** The value to check.
* `type` **([string](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) | [Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function) | null | [undefined](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/undefined) | [Array](#array))** The type of elements
##### Examples
Matching values
```javascript
// returns true
isArrayLikeOf([1, 2, 3], "number");
isArrayLikeOf({0: "a", 1: "b", length: 2}, "string");
```
Non-matching values
```javascript
// returns false
isArrayLikeOf([1, 2, "c"], "number");
isArrayLikeOf({a: 1, b: 2, length: 2}, "number");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a non-empty array-like object and all elements in the object have the specified type; <code>false</code> otherwise.
**Meta**
* **since**: 1.1.0
#### isPair
Determines whether the value is an array with two elements.
##### Parameters
* `value` **any** The value to check.
##### Examples
Pair values
```javascript
// returns true
isPair([1, 2]);
isPair([null, {}]);
```
Non-pair values
```javascript
// returns false
isPair([]);
isPair({a: 1, b: 2});
isPair("ab");
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is an array with two elements; <code>false</code> otherwise.
**Meta**
* **since**: 1.2.0
### Collection
#### isMap
* **See**: Map
Determines whether the value is a <code>Map</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Map values
```javascript
// returns true
isMap(new Map());
```
Non-Map values
```javascript
// returns false
isMap(new WeakMap());
isMap({a: 1, b: 2});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>Map</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isSet
* **See**: Set
Determines whether the value is a <code>Set</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Set values
```javascript
// returns true
isSet(new Set());
```
Non-Set values
```javascript
// returns false
isSet(new WeakSet());
isSet([1, 2, 3]);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>Set</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isWeakMap
* **See**: WeakMap
Determines whether the value is a <code>WeakMap</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
WeakMap values
```javascript
// returns true
isWeakMap(new WeakMap());
```
Non-WeakMap values
```javascript
// returns false
isWeakMap(new Map());
isWeakMap({a: 1, b: 2});
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>WeakMap</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
#### isWeakSet
* **See**: WeakSet
Determines whether the value is a <code>WeakSet</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
WeakSet values
```javascript
// returns true
isWeakSet(new WeakSet());
```
Non-WeakSet values
```javascript
// returns false
isWeakSet(new Set());
isWeakSet([1, 2, 3]);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>WeakSet</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.0.0
### Node
#### isNode
* **See**: Node
Determines whether the value is a DOM <code>Node</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Node objects
```javascript
// returns true
isNode(document);
isNode(document.createElement("div"));
isNode(new DocumentFragment());
```
Non-Node values
```javascript
// returns false
isNode(Node);
isNode(window);
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a DOM <code>Node</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.1.0
#### isElement
* **See**: Element
Determines whether the value is a DOM <code>Element</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
Element objects
```javascript
// returns true
isElement(document.createElement("div"));
```
Non-Element values
```javascript
// returns false
isElement(document);
isElement(window);
isElement(new DocumentFragment());
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a DOM <code>Element</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.1.0
#### isFragment
* **See**: DocumentFragment
Determines whether the value is a <code>DocumentFragment</code> object.
##### Parameters
* `value` **any** The value to check.
##### Examples
DocumentFragment objects
```javascript
// returns true
isFragment(new DocumentFragment());
```
Non-DocumentFragment values
```javascript
// returns false
isFragment(document);
isFragment(window);
isFragment(document.createElement("div"));
```
Returns **[boolean](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean)** <code>true</code> if the value is a <code>DocumentFragment</code> object; <code>false</code> otherwise.
**Meta**
* **since**: 1.1.0