is-what

Functions

• getType()
• isAnyObject()
• isArray()
• isBlob()
• isBoolean()
• isDate()
• isEmptyArray()
• isEmptyObject()
• isEmptyString()
• isError()
• isFile()
• isFullArray()
• isFullObject()
• isFullString()
• isFunction()
• isInstanceOf()
• isMap()
• isNaNValue()
• isNegativeNumber()
• isNull()
• isNullOrUndefined()
• isNumber()
• isObject()
• isObjectLike()
• isOneOf()
• isPlainObject()
• isPositiveNumber()
• isPrimitive()
• isPromise()
• isRegExp()
• isSet()
• isString()
• isSymbol()
• isType()
• isUndefined()
• isWeakMap()
• isWeakSet()

Type Aliases

• AnyAsyncFunction
• AnyClass
• AnyFunction
• PlainObject

function getType

getType: (payload: any) => string;

• Returns the object type of the given payload

  Parameter payload

  Returns

  {string}

function isAnyObject

isAnyObject: (payload: any) => payload is PlainObject;

• Returns whether the payload is an any kind of object (including special classes or objects with different prototypes)

  Parameter payload

  Returns

  {payload is PlainObject}

function isArray

isArray: (payload: any) => payload is any[];

• Returns whether the payload is an array

  Parameter payload

  Returns

  {payload is any[]}

function isBlob

isBlob: (payload: any) => payload is Blob;

• Returns whether the payload is a Blob

  Parameter payload

  Returns

  {payload is Blob}

function isBoolean

isBoolean: (payload: any) => payload is boolean;

• Returns whether the payload is a boolean

  Parameter payload

  Returns

  {payload is boolean}

function isDate

isDate: (payload: any) => payload is Date;

• Returns whether the payload is a Date, and that the date is valid

  Parameter payload

  Returns

  {payload is Date}

function isEmptyArray

isEmptyArray: (payload: any) => payload is [];

• Returns whether the payload is a an empty array

  Parameter payload

  Returns

  {payload is []}

function isEmptyObject

isEmptyObject: (
    payload: any
) => payload is { [x: string]: never; [x: number]: never; [x: symbol]: never };

• Returns whether the payload is a an empty object (excluding special classes or objects with other prototypes)

  Parameter payload

  Returns

  {payload is { [K in any]: never }}

function isEmptyString

isEmptyString: (payload: any) => payload is string;

• Returns whether the payload is ''

  Parameter payload

  Returns

  {payload is string}

function isError

isError: (payload: any) => payload is Error;

• Returns whether the payload is an Error

  Parameter payload

  Returns

  {payload is Error}

function isFile

isFile: (payload: any) => payload is File;

• Returns whether the payload is a File

  Parameter payload

  Returns

  {payload is File}

function isFullArray

isFullArray: (payload: any) => payload is any[];

• Returns whether the payload is a an array with at least 1 item

  Parameter payload

  Returns

  {payload is any[]}

function isFullObject

isFullObject: (payload: any) => payload is PlainObject;

• Returns whether the payload is a an empty object (excluding special classes or objects with other prototypes)

  Parameter payload

  Returns

  {payload is PlainObject}

function isFullString

isFullString: (payload: any) => payload is string;

• Returns whether the payload is a string, BUT returns false for ''

  Parameter payload

  Returns

  {payload is string}

function isFunction

isFunction: (payload: any) => payload is AnyFunction;

• Returns whether the payload is a function (regular or async)

  Parameter payload

  Returns

  {payload is AnyFunction}

function isInstanceOf

isInstanceOf: {
    <T extends AnyClass>(value: unknown, class_: T): value is T;
    <K extends GlobalClassName>(
        value: unknown,
        className: K
    ): value is (typeof globalThis)[K];
    (value: unknown, className: string): value is object;
};

• Checks if a value is an instance of a class or a class name. Useful when you want to check if a value is an instance of a class that may not be defined in the current scope. For example, if you want to check if a value is an OffscreenCanvas instance, you might not want to do the song and dance of using typeof OffscreenCanvas !== 'undefined' and then shimming OffscreenCanvas if the types aren't around.

  Parameter value

  The value to recursively check

  Parameter class_

  A string or class that the value should be an instance of

  Example 1

  if (isInstanceOf(value, 'OffscreenCanvas')) { // value is an OffscreenCanvas }

function isMap

isMap: (payload: any) => payload is Map<any, any>;

• Returns whether the payload is a Map

  Parameter payload

  Returns

  {payload is Map<any, any>}

function isNaNValue

isNaNValue: (payload: any) => payload is number;

• Returns whether the payload is literally the value NaN (it's NaN and also a number)

  Parameter payload

  Returns

  {payload is typeof NaN}

function isNegativeNumber

isNegativeNumber: (payload: any) => payload is number;

• Returns whether the payload is a negative number (but not 0)

  Parameter payload

  Returns

  {payload is number}

function isNull

isNull: (payload: any) => payload is null;

• Returns whether the payload is null

  Parameter payload

  Returns

  {payload is null}

function isNullOrUndefined

isNullOrUndefined: (payload: any) => payload is null;

• Returns true whether the payload is null or undefined

  Parameter payload

  Returns

  {(payload is null | undefined)}

function isNumber

isNumber: (payload: any) => payload is number;

• Returns whether the payload is a number (but not NaN)

  This will return false for NaN!!

  Parameter payload

  Returns

  {payload is number}

function isObject

isObject: (payload: any) => payload is PlainObject;

• Returns whether the payload is a plain JavaScript object (excluding special classes or objects with other prototypes)

  Parameter payload

  Returns

  {payload is PlainObject}

function isObjectLike

isObjectLike: <T extends PlainObject>(payload: any) => payload is T;

• Returns whether the payload is an object like a type passed in < >

  Usage: isObjectLike<{id: any}>(payload) // will make sure it's an object and has an id prop.

  T This must be passed in < >

  Parameter payload

  Returns

  {payload is T}

function isOneOf

isOneOf: {
    <A, B extends A, C extends A>(a: TypeGuard<A, B>, b: TypeGuard<A, C>): TypeGuard<
        A,
        B | C
    >;
    <A, B extends A, C extends A, D extends A>(
        a: TypeGuard<A, B>,
        b: TypeGuard<A, C>,
        c: TypeGuard<A, D>
    ): TypeGuard<A, B | C | D>;
    <A, B extends A, C extends A, D extends A, E extends A>(
        a: TypeGuard<A, B>,
        b: TypeGuard<A, C>,
        c: TypeGuard<A, D>,
        d: TypeGuard<A, E>
    ): TypeGuard<A, B | C | D | E>;
    <A, B extends A, C extends A, D extends A, E extends A, F extends A>(
        a: TypeGuard<A, B>,
        b: TypeGuard<A, C>,
        c: TypeGuard<A, D>,
        d: TypeGuard<A, E>,
        e: TypeGuard<A, F>
    ): TypeGuard<A, B | C | D | E | F>;
};

• A factory function that creates a function to check if the payload is one of the given types.

  Example 1

  import { isOneOf, isNull, isUndefined } from 'is-what'

  const isNullOrUndefined = isOneOf(isNull, isUndefined)

  isNullOrUndefined(null) // true isNullOrUndefined(undefined) // true isNullOrUndefined(123) // false

function isPlainObject

isPlainObject: (payload: any) => payload is PlainObject;

• Returns whether the payload is a plain JavaScript object (excluding special classes or objects with other prototypes)

  Parameter payload

  Returns

  {payload is PlainObject}

function isPositiveNumber

isPositiveNumber: (payload: any) => payload is number;

• Returns whether the payload is a positive number (but not 0)

  Parameter payload

  Returns

  {payload is number}

function isPrimitive

isPrimitive: (payload: any) => payload is string | number | boolean | symbol;

• Returns whether the payload is a primitive type (eg. Boolean | Null | Undefined | Number | String | Symbol)

  Parameter payload

  Returns

  {(payload is boolean | null | undefined | number | string | symbol)}

function isPromise

isPromise: (payload: any) => payload is Promise<any>;

• Returns whether the payload is a Promise

  Parameter payload

  Returns

  {payload is Promise}

function isRegExp

isRegExp: (payload: any) => payload is RegExp;

• Returns whether the payload is a regular expression (RegExp)

  Parameter payload

  Returns

  {payload is RegExp}

function isSet

isSet: (payload: any) => payload is Set<any>;

• Returns whether the payload is a Set

  Parameter payload

  Returns

  {payload is Set}

function isString

isString: (payload: any) => payload is string;

• Returns whether the payload is a string

  Parameter payload

  Returns

  {payload is string}

function isSymbol

isSymbol: (payload: any) => payload is symbol;

• Returns whether the payload is a Symbol

  Parameter payload

  Returns

  {payload is symbol}

function isType

isType: <T extends AnyFunction | AnyClass>(
    payload: any,
    type: T
) => payload is T;

• Does a generic check to check that the given payload is of a given type. In cases like Number, it will return true for NaN as NaN is a Number (thanks javascript!); It will, however, differentiate between object and null

  T

  Parameter payload

  Parameter type

  Returns

  {payload is T}

  Throws

  {TypeError} Will throw type error if type is an invalid type

function isUndefined

isUndefined: (payload: any) => payload is undefined;

• Returns whether the payload is undefined

  Parameter payload

  Returns

  {payload is undefined}

function isWeakMap

isWeakMap: (payload: any) => payload is WeakMap<any, any>;

• Returns whether the payload is a WeakMap

  Parameter payload

  Returns

  {payload is WeakMap<any, any>}

function isWeakSet

isWeakSet: (payload: any) => payload is WeakSet<any>;

• Returns whether the payload is a WeakSet

  Parameter payload

  Returns

  {payload is WeakSet}

type AnyAsyncFunction

type AnyAsyncFunction = (...args: any[]) => Promise<any>;

type AnyClass

type AnyClass = new (...args: any[]) => any;

type AnyFunction

type AnyFunction = (...args: any[]) => any;

type PlainObject

type PlainObject = Record<string | number | symbol, any>;