Global

Methods

getType(value) → {String}

More consistent variety of typeof. It returns a string such as Null, Undefined, Function, String, etc. These values mostly correspond to the value's constructor names.

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
String
Example
// getType() is not limited to the examples below
const v1 = null;
getType(v1); // "Null"

let v2;
getType(v2); // "Undefined"

const v3 = function() {};
getType(v3); // "Function", use isCallable() to cover async functions and generators as well

const v4 = async function() {};
getType(v4); // "AsyncFunction"

const v5 = function* generator(i) {};
getType(v5); // "GeneratorFunction"

const v6 = { foo: "bar" };
getType(v6); // "PlainObject", not "Object", as you may have expected

const v7 = new Map();
getType(v7); // "Map"

const v8 = new Set();
getType(v8); // "Set"

const v9 = new WeakMap();
getType(v9); // "WeakMap"

const v10 = new WeakSet();
getType(v10); // "WeakSet"

const v11 = new Date();
getType(v11); // "Date"

const v12 = new Error();
getType(v12); // "Error"

const v13 = new Promise(() => {});
getType(v13); // "Promise"

class CustomClass {}
const v14 = new CustomClass();
getType(v14); // "CustomClass"
getType(class CustomClass {}) // "Class", note the difference: CustomClass has not been initiated yet

isArray(value) → {Boolean}

Check if a value is an Array

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = [];
isArray(v1); // true 

const v2 = new Array(9);
isArray(v2); // true

const v3 = Array.from([1, 2, 3], x => x + x));
isArray(v3); // true

isAsyncFunction(value) → {Boolean}

Check if a value is an AsyncFunction

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = async(() => {});
isAsyncFunction(v1); // true 
isFunction(v1); // false, because this covers regular functions only

isBigInt(value) → {Boolean}

Check if a value is a BigInt

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const value = BigInt(123);
isBigInt(value); // true
isNumber(value); // false

isBlob(value) → {Boolean}

Check if a value is a Blob

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const obj = { foo: 'bar' };
const v1 = new Blob([JSON.stringify(obj, null, 2)], { type : 'application/json' });
isBlob(v1); // true

isBoolean(value) → {Boolean}

Check if a value is a Boolean

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = true;
isBoolean(v1); // true

isCallable(value) → {Boolean}

Check if a value is callable

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
class Foo {
    anyMethod(){...}
    static otherMethod(){...}
}
const fooObj = new Foo();
const v1 = fooObj.anyMethod;
isCallable(v1); // true

const v2 = Foo.otherMethod;
isCallable(v2); // true

const v3 = function () {}
isCallable(v3); // true

const v4 = function* generator(i) {};
isCallable(v4); // true

const v5 = async function () {};
isCallable(v5); // true

isCustomElement(value) → {Boolean}

Check if a value is a custom element

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
class MyElement extends HTMLElement {}
customElements.define("my-element", MyElement);

const v1 = document.createElement("my-element");
isCustomElement(v1); // true

isDate(value) → {Boolean}

Check if a value is a Date object

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = new Date();
isDate(v1); // true

isElement(value) → {Boolean}

Check if a value is a Element

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = document.createElement("div");
isElement(v1); // true

const v2 = document.createElementNS("http://www.w3.org/2000/svg", "svg");
isElement(v2); // true

const v3 = document.createElementNS("http://www.w3.org/1998/Math/MathML", "mrow");
isElement(v3); // true

class MyElement extends HTMLElement {}
customElements.define("my-element", MyElement);
const v4 = document.createElement("my-element");
isElement(v4); // true

isElementCollection(value) → {Boolean}

Check if a value is either a NodeList or an HTMLCollection

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = document.forms;
isElementCollection(v1); // true

const v2 = document.querySelectorAll("li");
isElementCollection(v2); // true

const v3 = Array.from(document.forms);
isElementCollection(v3); // false

const v4 = Array.from(document.querySelectorAll("li"));
isElementCollection(v4); // false

isEmptyObject(value) → {Boolean}

Check if a value is an empty plain object

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = {a:1, b:2};
isEmptyObject(v1); // false

const v2 = {};
isEmptyObject(v2); // true

isError(value) → {Boolean}

Check if a value is an Error

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = new Error();
isError(v1); // true

isFunction(value) → {Boolean}

Check if a value is a Function

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = function() {};
isFunction(v1); // true 

const v2 = new Function();
isFunction(v2); // true

const v3 = () => {};
isFunction(v3); // true

const v4 = function* generator(i) {};
isFunction(v4); // false
isGeneratorFunction(v4); // true

isGeneratorFunction(value) → {Boolean}

Check if a value is a GeneratorFunction

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const value = function* generator(i) {};
isGeneratorFunction(value); // true
isFunction(value); // false

isHtmlElement(value) → {Boolean}

Check if a value is an HTML element

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = document.createElement("div");
isHtmlElement(v1); // true

class MyElement extends HTMLElement {}
customElement("my-element", MyElement);

const v2 = document.createElement("my-element");
isHtmlElement(v2); // true

isIterable(value) → {Boolean}

Check if a value is an Iterable

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = [1, 2, 3];
isIterable(v1); // true 

const v2 = new Map();
isIterable(v2); // true 

const v3 = {};
isIterable(v3); // false

isMap(value) → {Boolean}

Check if a value is a Map

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = new Map();
isMap(v1); // true

isMathElement(value) → {Boolean}

Check if a value is a Math element

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = document.createElementNS("http://www.w3.org/1998/Math/MathML", "mrow");
isMathElement(v1); // true

isNull(value) → {Boolean}

Check if a value is null

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = null;
isNull(v1); // true

isNumber(value) → {Boolean}

Check if a value is a Number

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = 1;
isNumber(v1); // true

const v2 = new Number(1);
isNumber(v2); // true

const v3 = 1.1;
isNumber(v3); // true

const v4 = 42n;
isNumber(v4); // false
isBigInt(v4); // true

isPlainObject(value) → {Boolean}

Check if a value is a plain object

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const value = {a:1, b:2};
isPlainObject(value); // true
getType(value) // "PlainObject"

isPromise(value) → {Boolean}

Check if a value is a Promise

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = new Promise((resolve) => {});
isPromise(v1); // true

isRegExp(value) → {Boolean}

Check if a value is a RegExp

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = /regexp/;
isRegExp(v2); // true

const v3 = new RegExp("regexp", 'gi');
isRegExp(v3); // true

isSet(value) → {Boolean}

Check if a value is a Set

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = new Set();
isSet(v1); // true

isString(value) → {Boolean}

Check if a value is a String

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = "foo";
isString(v1); // true

const v2 = new String("foo");
isString(v2); // true

const v3 = String('foo');
isString(v3); // true

isSvgElement(value) → {Boolean}

Check if a value is an SVG element

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = document.createElementNS("http://www.w3.org/2000/svg", "svg");
isSvgElement(v1); // true

isSymbol(value) → {Boolean}

Check if a value is a Symbol

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = Symbol('foo');
isSymbol(v1); // true

isUndefined(value) → {Boolean}

Check if a value is undefined

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
let foo;
isUndefined(foo); // true

isWeakMap(value) → {Boolean}

Check if a value is a WeakMap

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = new WeakMap();
isWeakMap(v1); // true

isWeakSet(value) → {Boolean}

Check if a value is a WeakSet

Source:
Parameters:
Name Type Description
value *

The value to check
Returns:
Type:
Boolean
Example
const v1 = new WeakSet();
isWeakSet(v1); // true