https://github.com/wizard04wsu/javascript-type-testing
Improved JavaScript type testing
https://github.com/wizard04wsu/javascript-type-testing
javascript module type-testing
Last synced: 8 months ago
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Improved JavaScript type testing
- Host: GitHub
- URL: https://github.com/wizard04wsu/javascript-type-testing
- Owner: wizard04wsu
- Created: 2021-08-27T17:02:57.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2025-06-02T00:54:33.000Z (12 months ago)
- Last Synced: 2025-06-02T09:07:22.293Z (12 months ago)
- Topics: javascript, module, type-testing
- Language: JavaScript
- Homepage:
- Size: 52.7 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
# Improved JavaScript Type Testing
A robust alternative to type testing in vanilla JavaScript. Uses an expanded set of type names to simplify common tests.
See the [test page](https://wizard04wsu.github.io/javascript-type-testing/test/test.htm) for examples.
***Version 4 is not backwards compatible.***
## Syntax
> **is**(_value_)
The return value is an object that describes the argument.
| Member | Description
| - | -
| .type | The type name of _value_.
| .of(_class_) | Tests if _value_ is an instance of _class_.
| .all(_...descriptors_) | Takes descriptor names as arguments. Returns `true` if **all** of them apply to _value_.
| .any(_...descriptors_) | Takes descriptor names as arguments. Returns `true` if **any** of them apply to _value_.
| \[_descriptor_\] | Each [descriptor](#types-and-descriptors) property is a boolean that is `true` if it applies to _value_.
Enumerable properties of `is` are string constants of all the descriptor names. These can be used
in the `.all()` and `.any()` methods instead of string literals.
For example, these are equivalent:
> is(value).all("number", "object")
> is(value).all(is.number, is.object)
## Types and Descriptors
Types in this module do not distinguish between primitives and objects. For example, `5` and `new Number(5)` are both of type "number".
A descriptor is a boolean value that is `true` if it applies to the value being tested. Type names are included as descriptors. For example, `5` is associated with the _primitive_, _number_, and _finite_ descriptors, among others.
| Descriptor | Type Name | Primitive Values | Instances Of Classes
| - | - | - | -
| defined | | not undefined | `Object`
| **undefined** | yes | undefined |
| primitive | | any primitive value |
| **object** | yes[^1] | | `Object`
| objectish | | `null` | `Object`
| **null** | yes | `null` |
| nullish | | undefined, `null` |
| **boolean** | yes | `false`, `true` |
| false | | `false` |
| true | | `true` |
| falsy | | undefined, `null`, `false`, `0n`, `NaN`, `0`, `""` |
| truthy | | not a _falsy_ value | `Object`
| **symbol** | yes | a `Symbol` |
| **bigint** | yes | `0n`, `5n` |
| numberish | | `0`, `5`, `Infinity`, `NaN` | `Number`
| **nan** | yes | `NaN` | `Number` with value `NaN`
| **number** | yes | `0`, `5`, `Infinity` | `Number` excluding those with value `NaN`
| real[^2] | | `0`, `5` | `Number` with a finite number value
| finite | | `0`, `5` | `Number` with a finite number value
| infinite | | `Infinity` | `Number` with an infinite value
| **string** | yes | `""`, `"foo"` | `String`
| **array** | yes | `[]`, `[1,2]` | `Array`
| **map** | yes | | `Map`
| **set** | yes | | `Set`
| **weakmap** | yes | | `WeakMap`
| **weakset** | yes | | `WeakSet`
| empty | | `""`, `[]` | `String` or `Array` with `.length === 0`,
`Map` or `Set` with `.size === 0`
| nonempty | | `"foo"`, `[1,2]` | `String` or `Array` with `.length > 0`,
`Map` or `Set` with `.size > 0`
| **date** | yes | | `Date`
| **error** | yes | | `Error`
| **function** | yes | | `Function`
| **promise** | yes | | `Promise`
| **regex** | yes | | `Regex`
[^1]: The "object" type is only used for a value if no other type is appropriate.
[^2]: Deprecated. Use [_finite_](#finite) instead.