decorator-utils

Helpful utility functions to use when writing your own ES7 decorators.

Installation

Install the package with NPM:

$ npm install decorator-utils

Usage

A simple example:

import {DecoratorUtils} from "decorator-utils";
 
function decorator(target, name, descriptor) {
  let declarationType = DecoratorUtils.getDeclarationType(arguments);
 
  if (declarationType !== DecoratorUtils.declarationTypes.CLASS_METHOD) {
    throw new Error("Decorator must be applied to a class method declaration.");
  }
 
  // The rest of the decorator's logic...
}
 
@decorator // Error will be thrown.
class Dog {
  @decorator // Error will NOT be thrown.
  woof() {}
}

API

The package exposes a static class, DecoratorUtils, which has the following functions and properties:

getDeclarationType()

• A function that can be called from within a decorator to determine the type of declaration that is being targeted. Useful for guarding a decorator against certain declaration types.
• Parameters:
  • arguments - The arguments object of the decorator function. Just pass it through!
• Returns a value from DecoratorUtils.declarationTypes.

createDecorator()

• A function that produces a decorator that can only be applied to a subset of "supported" declaration types; all "unsupported" ones will throw an error. Handy if you want to create decorators in a factory-like manner.
• Parameters:
  • supportedDeclarationTypes - An array of values from DecoratorUtils.declarationTypes.
  • fn - A function that contains the rest of the decorator's logic.
• Returns a decorator (function).

declarationTypes

• A property describing the set of possible declaration types that a decorator can target, as key-value pairs of an object (String -> Symbol). To be used in conjunction with DecoratorUtils.getDeclarationType().
• Keys:
  • CLASS
  • CLASS_METHOD
  • CLASS_ACCESSOR
  • OBJECT_LITERAL_METHOD
  • OBJECT_LITERAL_ACCESSOR