@resreq/type-error-decorator

type-error-decorator

TypeError Decorator for JavaScript & TypeScript

When we make a TypeScript-based library, the compiled .d.ts will only work for TypeScript users, and if we need to add type checking for Vanilla JS users as well, we need to write redundant type of judgements.

This project provides some decorators that make it easy to add type checking to class.

Install

npm i @resreq/type-error-decorator

or

yarn add @resreq/type-error-decorator

Documentation

Get Started

Using decorators in class.

import { TypeClass, TypeMethod, TypeParam } from '@resreq/type-error-decorator'

@TypeClass
class Http {
  options? = {}
  constructor(@TypeParam('Object',false) options?: any) {
    this.options = options
  }

  @TypeMethod
  get(@TypeParam('String') url: any, options?: any) {}

  @TypeMethod
  post(@TypeParam('String|URL') url: any, @TypeParam('Object') options: any) {}
}

Testing your class, with an incorrect parameter type, will throw a TypeError.

new Http(1)
// TypeError: constructor arguments[0] must be Object

const http = new Http()
http.get(1)
// TypeError: get arguments[0] must be String

const http = new Http()
http.post(1, {})
// TypeError: post arguments[0] must be String or URL

const http = new Http()
http.post(new URL('https://www.example.com/'))
// TypeError: post arguments[1] is required

The decorator uses Symbol.toStringTag internally to compare types, so you can use all the built-in constructor names (Upper Camel Case) to define types.

For example:

@TypeParam('BigInt|RegExp|Symbol|Request|Response|...')

Decorators

TypeClass

• Arguments: No

• Usage:

  The check constructor must have @TypeClass added to the class.

TypeMethod

• Arguments: No

• Usage:

  The check method must have @TypeMethod added to the method.

TypeParam(type, required = true)

• Arguments:

  • {string} type
  • {Boolean?} required

• Usage:

  Add @TypeParam to the parameters of the method to set the type of check.

License

This project is licensed under the MIT License - see the LICENSE file for details