https://github.com/lamansky/is-instance-of
[Node.js] Like instanceof, but uses class name strings.
https://github.com/lamansky/is-instance-of
Last synced: about 1 year ago
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[Node.js] Like instanceof, but uses class name strings.
- Host: GitHub
- URL: https://github.com/lamansky/is-instance-of
- Owner: lamansky
- License: mit
- Created: 2018-02-14T21:18:36.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2021-11-08T11:44:02.000Z (over 4 years ago)
- Last Synced: 2025-03-31T07:22:03.446Z (about 1 year ago)
- Language: JavaScript
- Size: 5.86 KB
- Stars: 2
- Watchers: 1
- Forks: 1
- Open Issues: 1
-
Metadata Files:
- Readme: readme.md
- License: license.txt
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README
# is-instance-of
Like [`instanceof`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/instanceof), but uses class name strings. This means the module works cross-frame, [unlike `instanceof`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/instanceof$revision/1351859#instanceof_and_multiple_context_%28e.g._frames_or_windows%29).
## Installation
Requires [Node.js](https://nodejs.org/) 6.0.0 or above.
```bash
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
```javascript
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](https://github.com/lamansky/class-chain): Returns an object’s class and its ancestors.
* [isit](https://github.com/lamansky/isit): Tests a value’s type against a string like `'positive integer'` or `'non-empty map'`.