Benalu

A dynamic proxy for javascript. Provide a light weight proxy class generator with multiple interception.

About

The purpose of Benalu is provide a simple way to do a simple AOP in javascript. Benalu also useful for IOC container library that hasn't support for interception

Features

1. Can proxy a Function prototype or an object.

2. Can proxy method & property

3. Can add multiple interceptions

Installation

npm install benalu

How To Use It

Using benalu is very simple. You start building your proxy by using Benalu builder

var Benalu = require('benalu');

//declare the class
function MyObject(){}
MyObject.prototype.getNumber = function(){
    return 700;
}

//create instance
var myObject = new MyObject();

//make a proxy   
var proxy = Benalu.fromInstance(myObject)
    .addInterception(function(i) {
        //filter the invocation
        if(i.methodName == "getNumber"){
            //call the real method
            i.proceed();
            //override the return value
            i.returnValue = 300;
        }
    })
    .build();

var numResult = proxy.getNumber();
//numResult become 300 vs 700

Interception & Invocation

Interception in Benalu simply a callback function with single parameter of Invocation. Invocation consist of 3 important members:

1. methodName name of current invoked method. Usefull when you only want to intercept specific method of the class

2. parameters arguments passed to the invoked method. Usefull when you want to get information of the arguments passed to the method.

3. proceed() method to proceed current invocation. This method will invoke the method of the real object.

4. returnValue return value of the current invoked method. this member filled automatically after the proceed() method called. You can override the return value of current invocation by suplying a value to the returnValue member

Multiple Interception

Benalu also support multiple interception.

var Benalu = require('benalu');

function MyObject(){}
MyObject.prototype.getNumber = function(){
    console.log("The real method called");
    return 700;
}

var myObject = new MyObject();

var proxy = Benalu.fromInstance(myObject)
    .addInterception(function(i) {
        if(i.methodName == "getNumber"){
            console.log("First interceptor before proceed");
            i.proceed();
            console.log("First interceptor after proceed");
            i.returnValue = 300;
        }
    })
    .addInterception(function(i) {
        if(i.methodName == "getNumber"){
            console.log("Second interceptor before proceed");
            i.proceed();
            console.log("Second interceptor after proceed");
            i.returnValue = i.returnValue + 300;
        }
    })
    .build();

var numResult = proxy.getNumber();
//numResult = 600

Above code will write log in the console like below:

Second interceptor before proceed
First interceptor before proceed
The real method called
First interceptor after proceed
Second interceptor after proceed