JSPM

Introduction

A JavaScript type-checking library.

• version: 1.1.0
• author: Michael Ko <koyote130708@gmail.com>

If you find this library useful, please consider donating. Thank you. :)

Installation

npm i go-types

or

yarn add go-types

Usage

ES6

import Types from 'go-types'

Types.isArray([]);

or

import { isArray } from 'go-types';

isArray([]);

Node

const Types = require('go-types');

Types.isArray([]);

or

const { isArray } = require('go-types');

isArray([]);

Web browser

<script src="Types.js"></script>
<script>
    const { isArray } = Types;

    isArray([]);
</script>

Documentation

isUndefined

Determines whether the argument is undefined.

Parameters

• arg any The argument to check

Examples

Undefined values

// returns true
isUndefined(undefined);
isUndefined(void 0);

Non-undefined values

// returns false
isUndefined(null);
isUndefined(false);
isUndefined(0);
isUndefined("");
isUndefined(NaN);

Returns boolean true if the argument is undefined; false otherwise.

Meta

• since: 1.0.0

isNull

Determines whether the argument is null.

Parameters

• arg any The argument to check

Examples

Null values

// returns true
isNull(null);

Non-null values

// returns false
isNull(undefined);
isNull(false);
isNull(0);
isNull("");
isNull(NaN);

Returns boolean true if the argument is null; false otherwise.

Meta

• since: 1.0.0

isBoolean

• See: Types.isPrimitive
• See: Types.isObject
• See: Types.isTypeOf

Determines whether the argument is a primitive boolean or Boolean object. Note: To check exclusively, use with isPrimitive or isObject respectively or use isTypeOf instead.

Parameters

• arg any The argument to check

Examples

Boolean values

// returns true
isBoolean(true);
isBoolean(new Boolean(true));

Non-boolean values

// returns false
isBoolean(1);
isBoolean("true");

Returns boolean true if the argument is a primitive boolean or Boolean object; false otherwise.

Meta

• since: 1.0.0

isNumber

• See: Types.isPrimitive
• See: Types.isObject
• See: Types.isTypeOf

Determines whether the argument is a primitive number or Number object which includes the "special" numbers +Infinity, -Infinity and NaN. Note: To check exclusively, use with isPrimitive or isObject respectively or use isTypeOf instead.

Parameters

• arg any The argument to check

Examples

Number values

// returns true
isNumber(1);
isNumber(-12.34);
isNumber(new Number(1));
isNumber(Infinity);
isNumber(NaN);

Non-number values

// returns false
isNumber("1");
isNumber(true);

Returns boolean true if the argument is a primitive number or Number object; false otherwise.

Meta

• since: 1.0.0

isString

• See: Types.isPrimitive
• See: Types.isObject
• See: Types.isTypeOf

Determines whether the argument is a primitive string or String object. Note: To check exclusively, use with isPrimitive or isObject respectively or use isTypeOf instead.

Parameters

• arg any The argument to check

Examples

String values

// returns true
isString("1");
isString(new String("abc"));

Non-string values

// returns false
isString(1);
isString(["a", "b"]);

Returns boolean true if the argument is a primitive string or String object; false otherwise.

Meta

• since: 1.0.0

isPrimitive

Determines whether the argument is a primitive value.

Parameters

• arg any The argument to check

Examples

Primitive values

// returns true
isPrimitive(undefined);
isPrimitive(null);
isPrimitive(false);
isPrimitive(0);
isPrimitive("abc");
isPrimitive(Symbol("abc"));
isPrimitive(BigInt(1234567890));

Non-primitive values

// returns false
isPrimitive(new Number(1));
isPrimitive([1, 2, 3]);
isPrimitive(function () {});

Returns boolean true if the argument is a primitive value; false otherwise.

Meta

• since: 1.0.0

isObject

Determines whether the argument is an object.

Parameters

• arg any The argument to check

Examples

Object values

// returns true
isObject({a: 1, b: 2});
isObject(["a", "b"]);
isObject(new Object());
isObject(new Number(1));
isObject(function() {});

Non-object values

// returns false
isObject(null);
isObject("abc");
isObject(Symbol("abc"));
isObject(1);
isObject(BigInt(1));

Returns boolean true if the argument is an object; false otherwise.

Meta

• since: 1.0.0

isPlainObject

Determines whether the argument is a plain object created using object literal or new Object().

Parameters

• arg any The argument to check

Examples

Plain object values

// returns true
isPlainObject({a: 1, b: 2});
isPlainObject(new Object());

Non-plain-object values

// returns false
isPlainObject(null);
isPlainObject("abc");
isPlainObject([1, 2]);
isPlainObject(new Number(1));

Returns boolean true if the argument is a plain object; false otherwise.

Meta

• since: 1.0.0

isFunction

Determines whether the argument is a function.

Parameters

• arg any The argument to check

Examples

Function values

// returns true
isFunction(function() {});
isFunction(Object);

Non-function values

// returns false
isFunction(null);
isFunction(new Object());
isFunction("function() {}");

Returns boolean true if the argument is a function; false otherwise.

Meta

• since: 1.0.0

isArray

Determines whether the argument is an array.

Parameters

• arg any The argument to check

Examples

Array values

// returns true
isArray(["a", "b"]);
isArray(new Array());

Non-array values

// returns false
isArray("abc");
isArray({length: 0});
isArray(new Int8Array());

Returns boolean true if the argument is an array; false otherwise.

Meta

• since: 1.0.0

isArrayLike

Determines whether the argument is an array-like object with a "length" property.

Parameters

• arg any The argument to check

Examples

Array-like objects

// returns true
isArrayLike([]);
isArrayLike("abc");
isArrayLike({length: 0});
isArrayLike(new Int8Array());

Non-array-like values

// returns false
isArrayLike({});
isArrayLike(new Set());
isArrayLike(Array);

Returns boolean true if the argument is an array-like object; false otherwise.

Meta

• since: 1.0.0

isArrayOf

Determines whether the argument is an array of the specified type and has at least one element.

Parameters

• arg any The argument to check
• type (string | Function | null | undefined | Array) the type of elements

Examples

Matching values

// returns true
isArrayOf([1, 2, 3], "number");
isArrayOf(["a", "b", null], ["string", null]);
isArrayOf([{a: 1}, {b: 2}], Object);

Non-matching values

// returns false
isArrayOf([1, 2, "c"], "number");
isArrayOf([], undefined);

Returns boolean true if the argument is an array and and all elements in the array are of the specified type; false otherwise.

Meta

• since: 1.1.0

isArrayLikeOf

Determines whether the argument is an array-like object of the specified type and has at least one element.

Parameters

• arg any The argument to check
• type (string | Function | null | undefined | Array) the type of elements

Examples

Matching values

// returns true
isArrayLikeOf([1, 2, 3], "number");
isArrayLikeOf({0: "a", 1: "b", length: 2}, "string");

Non-matching values

// returns false
isArrayLikeOf([1, 2, "c"], "number");
isArrayLikeOf({a: 1, b: 2, length: 2}, "number");

Returns boolean true if the argument is an array-like object and all elements in the array are of the specified type; false otherwise.

Meta

• since: 1.1.0

isDate

• See: Date

Determines whether the argument is a Date object.

Parameters

• arg any The argument to check

Examples

Date values

// returns true
isDate(new Date());
isDate(new Date(""));

Non-date values

// returns false
isDate("2001-01-01T00:00:00.000Z");
isDate(978307200000);

Returns boolean true if the argument is a Date object; false otherwise.

Meta

• since: 1.0.0

isRegExp

• See: RegExp

Determines whether the argument is a RegExp object.

Parameters

• arg any The argument to check

Examples

RegExp values

// returns true
isRegExp(/[a-z]/);
isRegExp(new RegExp("[a-z]"));

Non-RegExp values

// returns false
isRegExp("[a-z]");
isRegExp("/[a-z]/");

Returns boolean true if the argument is a RegExp object; false otherwise.

Meta

• since: 1.0.0

isPromise

• See: Promise

Determines whether the argument is a Promise object.

Parameters

• arg any The argument to check

Examples

Promise values

// returns true
isPromise(new Promise(resolve, reject));
isPromise(Promise.resolve());
isPromise(Promise.reject());

Non-promise values

// returns false
isPromise({then: function() {}, catch: function() {}});

Returns boolean true if the argument is a Promise object; false otherwise.

Meta

• since: 1.0.0

isPromiseLike

• See: Promise API Reference

Determines whether the argument is an object that defines then and catch methods.

Parameters

• arg any The argument to check

Examples

Promise-like objects

// returns true
isPromiseLike(new Promise(resolve, reject));
isPromiseLike({then: function() {}, catch: function() {}});

Non-promise-like values

// returns false
isPromiseLike({then: function() {}});
isPromiseLike({then: true, catch: true});

Returns boolean true if the argument is a Promise-like object; false otherwise.

Meta

• since: 1.0.0

isThenable

Determines whether the argument is an object that defines a then method.

Parameters

• arg any The argument to check

Examples

Thenable objects

// returns true
isThenable(new Promise(resolve, reject));
isThenable({then: function() {}});

Non-thenable values

// returns false
isThenable(null);
isThenable({then: true});

Returns boolean true if the argument is a thenable object; false otherwise.

Meta

• since: 1.1.0

isSymbol

• See: Symbol

Determines whether the argument is a Symbol.

Parameters

• arg any The argument to check

Examples

Symbol values

// returns true
isSymbol(Symbol("abc"));

Non-Symbol values

// returns false
isSymbol("abc");
isSymbol(/[a-z]/);

Returns boolean true if the argument is a Symbol; false otherwise.

Meta

• since: 1.0.0

isBigInt

• See: BigInt

Determines whether the argument is a BigInt value.

Parameters

• arg any The argument to check

Examples

BigInt values

// returns true
isBigInt(BigInt(1));
isBigInt(BigInt(-1234567890));

Non-BigInt values

// returns false
isBigInt(Number.MAX_VALUE);
isBigInt(Infinity);
isBigInt(NaN);
isBigInt("1n");

Returns boolean true if the argument is a BigInt value; false otherwise.

Meta

• since: 1.0.0

isMap

• See: Map

Determines whether the argument is a Map object.

Parameters

• arg any The argument to check

Examples

Map values

// returns true
isMap(new Map());

Non-Map values

// returns false
isMap(new WeakMap());
isMap({a: 1, b: 2});

Returns boolean true if the argument is a Map object; false otherwise.

Meta

• since: 1.0.0

isSet

• See: Set

Determines whether the argument is a Set object.

Parameters

• arg any The argument to check

Examples

Set values

// returns true
isSet(new Set());

Non-Set values

// returns false
isSet(new WeakSet());
isSet([1, 2, 3]);

Returns boolean true if the argument is a Set object; false otherwise.

Meta

• since: 1.0.0

isWeakMap

• See: WeakMap

Determines whether the argument is a WeakMap object.

Parameters

• arg any The argument to check

Examples

WeakMap values

// returns true
isWeakMap(new WeakMap());

Non-WeakMap values

// returns false
isWeakMap(new Map());
isWeakMap({a: 1, b: 2});

Returns boolean true if the argument is a WeakMap object; false otherwise.

Meta

• since: 1.0.0

isWeakSet

• See: WeakSet

Determines whether the argument is a WeakSet object.

Parameters

• arg any The argument to check

Examples

WeakSet values

// returns true
isWeakSet(new WeakSet());

Non-WeakSet values

// returns false
isWeakSet(new Set());
isWeakSet([1, 2, 3]);

Returns boolean true if the argument is a WeakSet object; false otherwise.

Meta

• since: 1.0.0

isIterable

• See: Iterable

Determines whether the argument is iterable. An iterable implements the Symbol.iterator method and can be used in a for..of operator.

Parameters

• arg any The argument to check

Examples

Iterable values

// returns true
isIterable([1, 2, 3]);
isIterable("abc");
isIterable(new Map());
isIterable(new Set());
isIterable({[Symbol.iterator]: function() {}});

Non-iterable values

// returns false
isIterable({a: 1, b: 2});
isIterable(12345);

Returns boolean true if the argument is iterable; false otherwise.

Meta

• since: 1.0.0

isError

• See: Error

Determines whether the argument is an Error object.

Parameters

• arg any The argument to check

Examples

Error objects

// returns true
isError(new Error("Validation error"));
isError(new TypeError("Expected a number, but found: " + arg));

Non-Error values

// returns false
isError(null);
isError(NaN);
isError(Promise.reject());
isError({name: "TypeError", message: "Expected a number"});

Returns boolean true if the argument is an Error object; false otherwise.

Meta

• since: 1.0.0

isNode

• See: Node

Determines whether the argument is a DOM Node object.

Parameters

• arg any The argument to check

Examples

Node objects

// returns true
isNode(document);
isNode(document.createElement("div"));
isNode(new DocumentFragment());

Non-Node values

// returns false
isNode(Node);
isNode(window);

Returns boolean true if the argument is a DOM Node object; false otherwise.

Meta

• since: 1.1.0

isElement

• See: Element

Determines whether the argument is a DOM Element object.

Parameters

• arg any The argument to check

Examples

Element objects

// returns true
isElement(document.createElement("div"));

Non-Element values

// returns false
isElement(document);
isElement(window);
isElement(new DocumentFragment());

Returns boolean true if the argument is a DOM Element object; false otherwise.

Meta

• since: 1.1.0

isFragment

• See: DocumentFragment

Determines whether the argument is a DocumentFragment object.

Parameters

• arg any The argument to check

Examples

DocumentFragment objects

// returns true
isFragment(new DocumentFragment());

Non-DocumentFragment values

// returns false
isFragment(document);
isFragment(window);
isFragment(document.createElement("div"));

Returns boolean true if the argument is a DocumentFragment object; false otherwise.

Meta

• since: 1.1.0

isNullish

• See: undefined
• See: null

Determines whether the argument is null or undefined.

Parameters

• arg any The argument to check

Examples

Nullish values

// returns true
isNullish();
isNullish(undefined);
isNullish(void 0);

Non-nullish values

// returns false
isNullish(null);
isNullish(false);
isNullish(0);
isNullish("");
isNullish([]);
isNullish(NaN);

Returns boolean true if the argument is null or undefined; false otherwise.

Meta

• since: 1.0.0

isTruthy

Determines whether the argument 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 false, 0, "", undefined, null and NaN.

Parameters

• arg any The argument to check

Examples

Truthy values

// returns true
isTruthy(true);
isTruthy(1);
isTruthy("false");
isTruthy(new Boolean(false));
isTruthy({});

Non-truthy values

// returns false
isTruthy(false);
isTruthy(0);
isTruthy("");
isTruthy(undefined);
isTruthy(null);
isTruthy(NaN);

Returns boolean true if the argument is a truthy value; false otherwise.

Meta

• since: 1.0.0

isFalsy

Determines whether the argument is a falsy value which can be one of the following:

• false
• 0
• ""
• undefined
• null
• NaN

Parameters

• arg any The argument to check

Examples

Falsy values

// returns true
isFalsy(false);
isFalsy(0);
isFalsy("");
isFalsy(undefined);
isFalsy(null);
isFalsy(NaN);

Non-falsy values

// returns false
isFalsy(true);
isFalsy(1);
isFalsy("false");
isFalsy(new Boolean(false));
isFalsy({});

Returns boolean true if the argument is a falsy value; false otherwise.

Meta

• since: 1.0.0

isEmpty

Determines whether the argument is an empty value which can be one of the following:

• null
• undefined
• An empty string whose length is zero
• An empty array whose length is zero
• An empty object which has no enumerable keys

Parameters

• arg any The argument to check

Examples

Empty values

// returns true
isEmpty(null);
isEmpty(undefined);
isEmpty("");
isEmpty([]);
isEmpty({});

Non-empty values

// returns false
isEmpty(" ");
isEmpty(0);
isEmpty(false);
isEmpty([null]);
isEmpty({a: ""});
isEmpty(NaN);

Returns boolean true if the argument is an empty value; false otherwise.

Meta

• since: 1.0.0

isBlank

Determines whether the argument is a blank value which can be one of the following:

• null
• undefined
• A blank string which is empty or has only space characters
• A blank array which has no elements or has only undefined or null values
• A blank object which has no enumerable keys or has only undefined or null values

Parameters

• arg any The argument to check

Examples

Blank values

// returns true
isBlank(null);
isBlank(undefined);
isBlank(" \t\n ");
isBlank([undefined, null]);
isBlank({a: null, b: undefined})

Non-blank values

// returns false
isBlank(0);
isBlank(false);
isBlank(" a ");
isBlank([""]);
isBlank({a: ""});
isBlank(NaN);

Returns boolean true if the argument is a blank value; false otherwise.

Meta

• since: 1.0.0

isNumeric

Determines whether the argument is a numeric value which can be one of the following:

• Primitive number or Number object that has a finite value
• Primitive string or String object that represents a finite number
• BigInt

Parameters

• arg any The argument to check

Examples

Numeric values

// 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

// returns false
isNumeric(NaN);
isNumeric(Infinity);
isNumeric("12000n");
isNumeric("1*2");

Returns boolean true if the argument is a numeric value; false otherwise.

Meta

• since: 1.0.0

isInteger

Determines whether the argument is an integer (a primitive number or Number object).

Parameters

• arg any The argument to check

Examples

Integer values

// returns true
isInteger(1);
isInteger(new Number(1));

Non-integer values

// returns false
isInteger(isInteger(0.1));
isInteger("1");
isInteger(Infinity);
isInteger(NaN);

Returns boolean true if the argument is an integer; false otherwise.

Meta

• since: 1.0.0

isSafeInteger

• See: Number.isSafeInteger

Determines whether the argument is a safe integer (a primitive number or Number object). A safe integer is an integer that:

• can be exactly represented as an IEEE-754 double precision number, and
• whose IEEE-754 representation cannot be the result of rounding any other integer to fit the IEEE-754 representation.

Parameters

• arg any The argument to check

Examples

Safe integer values

// returns true
isSafeInteger(1);
isSafeInteger(Number.MAX_SAFE_INTEGER);
isSafeInteger(Number.MIN_SAFE_INTEGER);

Non-safe-integer values

// returns false
isSafeInteger(0.1);
isSafeInteger("1");
isSafeInteger(Number.MIN_SAFE_INTEGER - 1);
isSafeInteger(NaN);

Returns boolean true if the argument is a safe integer; false otherwise.

Meta

• since: 1.1.0

isFloat

Determines whether the argument is a primitive number or Number object whose value is with a decimal point.

Parameters

• arg any The argument to check

Examples

Decimal values

// returns true
isFloat(0.1);
isFloat(-1234.56789);
isFloat(new Number(0.1));

Non-decimal values

// returns false
isFloat(1);
isFloat(1.0);
isFloat("1.2");

Returns boolean true if the argument is a number with a decimal point; false otherwise.

Meta

• since: 1.0.0

isFinite

• See: isFinite

Determines whether the argument is a primitive number or Number object whose value is a finite number.

Parameters

• arg any The argument to check

Examples

Finite values

// returns true
isFinite(0);
isFinite(-0.1);
isFinite(Number.MAX_VALUE);

Non-finite values

// returns false
isFinite(Infinity);
isFinite("1");
isFinite(NaN);

Returns boolean true if the argument is a finite number; false otherwise.

Meta

• since: 1.0.0

isInfinite

• See: isFinite

Determines whether the argument is a primitive number or Number object that represents positive or negative infinity.

Parameters

• arg any The argument to check

Examples

Infinite values

// returns true
isInfinite(Infinity);
isInfinite(Number.NEGATIVE_INFINITY);

Non-infinite values

// returns false
isInfinite(Number.MAX_VALUE);
isInfinite(NaN);

Returns boolean true if the argument is a number that represents positive or negative infinity; false otherwise.

Meta

• since: 1.0.0

isNaN

• See: Number.isNaN

Determines whether the argument is a primitive number or a Number object whose value is NaN. NaN is the only value in javascript that is not equal to itself.

Parameters

• arg any The argument to check

Examples

NaN values

// returns true
isNaN(NaN);
isNaN(new Number(NaN));
isNaN(0/0);

Non-NaN values

// returns false
isNaN(undefined);
isNaN(null);
isNaN("NaN");
isNaN(Infinity);

Returns boolean true if the argument is NaN; false otherwise.

Meta

• since: 1.0.0

isTypeOf

Determines whether the argument is the specified type. Based on the type value, it will perform the following:

• string - checks if the type matches (case-sensitive) using the typeof operator.
• function - checks if the argument is an instance of the function/class using the instanceof operator.
• null/undefined - checks if the argument is equal to the type using the strict equality (===) operator.
• array - checks if there is any matching type in the array by calling this function with the same argument and each type value.

Parameters

• arg any The argument to check
• type (string | Function | null | undefined | Array)

Examples

Matching type values

// returns true
isTypeOf(1, "number");
isTypeOf({a: 1}, Object);
isTypeOf("abc", ["string", undefined]);

Non-matching type values

// returns false
isTypeOf(1, "boolean");
isTypeOf("", String);
isTypeOf(null, ["string", String]);

Returns boolean true if the argument is of the type; false otherwise.

Meta

• since: 1.0.0