A simple AOP implementation for Node. It works either with standalone functions or with object methods. It can be used on the client-side with Browserify too.

Example

aspectjs.after(myGreatObject, "someMethod").add(myGreatAdvice, "someOtherMethod");

// Thereafter whenever myGreatObject.someMethod is called, 
// myGreatAdvice.someOtherMethod will be called automatically afterward.

API Documentation

All of the following methods of aspectjs return an "advice object" that contains an add() method, which applies the advice setup in after(), before(), or around().

Methods of aspectjs

before(joinpoint, [methodname])

Will add advice before the specified join point, once add() is called. The join point can be either a function or an object followed by a method name. Returns the advice object.

after(joinpoint, [methodname])

Will add the advice after the specified join point, once add() is called.
The join point can be either a function or an object followed by a method name.
Returns the he advice object.

around(joinpoint, [methodname])

Adds the advice round the specified join point, once add() is called.
The join point can be either a function or an object followed by a method name.
Returns the advice object.

These method requires an advice function/method that takes an Invocation object. Within the advice body, invocation.proceed() should be called where the joinpoint should occur. The advice is applied only after add() is called on the returned advice object.

// Example advice object for around advice
adviser = {adviseFunction: function(invocation){
    // Some code goes here.
    invocation.proceed();   // Calls the original function.
    // Some more code goes here.
}};

Methods of the advice object

add([thisArg,] function|string)

Returns the new function that wraps the original function passed to before(), after(), or around().

Usage

Standalone functions

Both the advice and joinpoints can be standalone functions:

aspectjs.before(joinpoint).add(advice).

Or the advice can be an object method, while the joinpoint is standalone:

aspectjs..after(joinpoint).add(advice, 'methodname')

Object methods

Both the advice and joinpoint can be object methods:

aspectjs.before(joinpointObj, 'methodname').add(adviceObj, 'methodname')

Examples

Before advice

const before = require('aspectjs').before;
let addAdvice = require("aspectjs").addAdvice;

let advised, adviser, result;
advised = {
   add: function(increment){this.left += increment; }, 
   id: 'test', 
   left: 32, 
   top: 43
};
adviser = {
   override: function(increment){ advised.left = increment; }
};

before(advised, "add").add(adviser, "override");
advised.add(2);  // Should equal 4.        

Around advice

const around = require('aspectjs').around;
let advised, adviser, result;
advised = {
   add: function(increment){
       this.left += increment; 
   }, 
   id: 'test', 
   left: 32, 
   top: 43
};

// The advice function/method should take an Invocation object as input.
// Then invocation.proceed() should be called where the joinpoint occurs.
adviser = {
   override: function(invocation){
       advised.left += 5; // 37
       invocation.proceed(); // 39
       advised.left -= 19;
   }
};

around(advised, "add").add(adviser, "override");

Links

• NPM: https://www.npmjs.com/package/aspectjs/