Proxify-Objects

Uses Proxies to create computed values

Install

$ npm install --save proxify-objects

Usage

const makeNewProxy = require( 'proxify-objects' );

let circle = makeNewProxy({ radius: 3, area: 2 }, {
    area(obj) {
        return obj.radius * obj.radius * Math.PI
    }
})

circle.radius = 10
circle.area
//=> 314.1592653589793

What it does

It allows you to make computabe properties that look like normal properties. In the example above area depends on radius so when we set the radius it updates the area according to the function specified in the second parameter of the function.

Can it do more?

Of course it can.

circle = makeNewProxy({ radius: 3, area: 2 }, {
    area(obj) {
        return obj.radius * obj.radius * Math.PI
    }
}, {
    area(target, property, value) {
        circle.radius = Math.sqrt(value / Math.PI)
        return value
    }
})

circle.area = 100
circle.radius
//=> 5.641895835477563

What did that do?

It just created a bidirectional relationship between the area and radius of the circle; now the radius has just been updated based on the area of the circle. So now whenever the radius is updated it updates the area and when the area is updated it updates the radius.

API

makeNewProxy(objectToBeProxied, gettersObject, settersObject)

objectToBeProxied:

Just a Plain Ol JavaScript Object that may or may not have all the properties you wish to have computed.

gettersObject:

Another PoJo with keys equal to the properties you wish to have computed and values of the function you wish to compute with. The function will be called with the function signature:

function( proxyObjectItself)

returning

Anything you return within this function will be used as the computed value without restriction.

defaultCase

A special key with the name defaultCase can be called whenever a key is not on the original object. This can be used dynamically create properties to be read from. It is called with the function signature:

function( proxyObject, keyBeingCalledFor )

settersObject:

Another PoJo with keys equal to the properties you want to control the setting of; with values of the functionl you wish to create that setting with. The function will be called with the function signature:

function( proxyObjectItself, keyBeingAttemptedToSet, valueBeingAttemptedToSet )

Returning

If what is returned is Undefined or no return is specified: No additional assignment on the object will be made. If what is returned is anything but Undefined: Whatever is returned will be assigned to the key specified and its value will be whatever is returned from that function.

defaultCase

A special key with the name defaultCase can be called whenever a key is not on the original object. This can be used dynamically create properties to be read from. It is called with the function signature:

function( proxyObjectItself, keyBeingAttemptedToBeSet, valueAttemptedToBeingSet, originalPoJoObjectToAvoidRecursion )

Note: anything set on the original PoJo Object is automatically available to the object returned from making the proxy.