attrash-islam / aspect.js

Aspect-oriented programming library for the future generations...

Introduction

Library for aspect-oriented programming with JavaScript, which takes advantage of ECMAScript 2016 decorators syntax.

For further reading on decorators, take a look at the spec.

Blog post, introduction to the AOP and the library could be found here.

Talk from AngularConnect.

Sample usage

import {beforeMethod, Wove, Metadata} from 'aspect.js';

class LoggerAspect {
  @beforeMethod({
    classNamePattern: /^Article/,
    methodNamePattern: /^(get|set)/
  })
  invokeBeforeMethod(meta: Metadata) {
    // meta.woveMetadata == { bar: 42 }
    console.log(`Inside of the logger. Called ${meta.className}.${meta.method.name} with args: ${meta.method.args.join(', ')}.`);
  }
}

class Article {
  id: number;
  title: string;
  content: string;
}

@Wove({ bar: 42 })
class ArticleCollection {
  articles: Article[] = [];
  getArticle(id: number) {
    console.log(`Getting article with id: ${id}.`);
    return this.articles.filter(a => {
      return a.id === id;
    }).pop();
  }
  setArticle(article: Article) {
    console.log(`Setting article with id: ${article.id}.`);
    this.articles.push(article);
  }
}

new ArticleCollection().getArticle(1);

// Result:
// Inside of the logger. Called ArticleCollection.getArticle with args: 1.
// Getting article with id: 1.

In case you're using aspect.js in a browser environment the minifier may break the annotated code because of the performed mangling. In order to handle this problem you can use:

class LoggerAspect {
  @beforeMethod({
    classes: [ArticleCollection],
    methods: [ArticleCollection.prototype.getArticle, ArticleCollection.prototype.setArticle]
  })
  invokeBeforeMethod(meta: Metadata) {
    // meta.woveMetadata == { bar: 42 }
    console.log(`Inside of the logger. Called ${meta.className}.${meta.method.name} with args: ${meta.method.args.join(', ')}.`);
  }
}

class ArticleCollection {
  getArticle(id: number) {...}
  setArticle(article: Article) {...}
}

In this case you can omit the @Wove decorator.

This way, by explicitly listing the classes and methods which should be woven, you can prevent the unwanted effect of mangling.

API

The library offers the following combinations of advices and joint points:

Method calls

• beforeMethod(MethodSelector) - invoked before method call
• afterMethod(MethodSelector) - invoked after method call
• aroundMethod(MethodSelector) - invoked around method call
• onThrowOfMethod(MethodSelector) - invoked on throw of method call
• asyncOnThrowOfMethod(MethodSelector) - invoked on throw of async method call

Static method calls

• beforeStaticMethod(MethodSelector) - invoked before static method call
• afterStaticMethod(MethodSelector) - invoked after static method call
• aroundStaticMethod(MethodSelector) - invoked around static method call
• onThrowOfStaticMethod(MethodSelector) - invoked on throw of static method call
• asyncOnThrowOfStaticMethod(MethodSelector) - invoked on throw of async static method call

Accessors

• beforeSetter(MemberSelector) - invoked before setter call
• afterSetter(MemberSelector) - invoked after setter call
• aroundSetter(MemberSelector) - invoked around setter call
• onThrowOfSetter(MemberSelector) - invoked on throw of setter call
• asyncOnThrowOfSetter(MemberSelector) - invoked on throw of async setter call
• beforeGetter(MemberSelector) - invoked before getter call
• afterGetter(MemberSelector) - invoked after getter call
• aroundGetter(MemberSelector) - invoked around getter call
• onThrowOfGetter(MemberSelector) - invoked on throw of getter call
• asyncOnThrowOfGetter(MemberSelector) - invoked on throw of async getter call

MethodSelector

export interface MethodSelector {
  classNamePattern?: RegExp;
  methodNamePattern?: RegExp;
  classes?: Function[];
  methods?: Function[];
}

MemberSelector

export interface MemberSelector {
  classNamePattern: RegExp;
  fieldNamePattern: RegExp;
  classes?: Function[];
  methods?: PropertyDescriptor[];
}

Metadata

export class Metadata {
  public method: MethodMetadata;
  public className: string;
  public woveMetadata: any;
}

MethodMetadata

export class MethodMetadata {
  public proceed: boolean;
  public name: string;
  public args: any[];
  public context: any;
  public result: any;
  public exception: any;
  public invoke: (...args: any[]) => any;
}

Demo

git clone https://github.com/mgechev/aop.js --depth 1
npm install -g ts-node
ts-node demo/index.ts

Roadmap

• Tests
• Type annotations and DTS generation
• Aspect factories
  • Generic aspects
• Implement the following advices:
  • Before
  • After
    • Throwing
    • Returning
  • Around
• Implement the following joint points:
  • Method execution
  • Static method execution
  • Constructor execution
  • Filed get
  • Field set

License

MIT