is-instance-of

Like instanceof, but uses class name strings. This means the module works cross-frame, unlike instanceof.

Installation

Requires Node.js 6.0.0 or above.

npm i is-instance-of

API

The module exports a single function.

Parameters

1. Bindable: x (object): The object that may or may not be an instance of the specified class(es).
2. classes (function, string, or array of functions/strings): Class names to look for in x’s prototype chain. (If one or more functions are provided, their names will be used, so that the check works cross-realm.)
3. Object argument:
   • Optional: ci (boolean): If true, class names will be compared case-insensitively. Defaults to false.

Return Value

• true if x has any one of the classes in its prototype chain.
• false otherwise.

Examples

const isInstanceOf = require('is-instance-of')
 
isInstanceOf(new Date(), 'Date') // true
isInstanceOf(new Date(), Date) // true
 
// Case sensitivity / insensitivity
isInstanceOf(new Date(), 'date') // false
isInstanceOf(new Date(), 'date', {ci: true}) // true
 
// Only one class name needs to be matched for true to be returned
isInstanceOf(new Error(), ['Error', 'Date', RegExp]) // true
 
// Supports the bind operator
[]::isInstanceOf('Array') // true

Nota Bene

This module’s strength is also its weakness. The module will consider Date in one frame/context to be equivalent to Date in another context, so long as they have the same name. The advantage of this approach is that this allows for cross-frame type checks. The disadvantage is that Date could be a completely different class in the other context and this module wouldn’t know the difference.

Related

• class-chain: Returns an object’s class and its ancestors.
• isit: Tests a value’s type against a string like 'positive integer' or 'non-empty map'.