object-change v0.0.11

object-change

Simple utility to be able to attach listeners to events that fired when an object property changes

Overview

Basically using this utility on any plain object will create a new object that is an instance of a dispatcher and that will fire events when the "observed" properties change.

Install

npm i --save object-change

Interface

objChange( obj:Object, properties:Array ):dispatcher

Parameters

• obj:Object: The object with the initial values for the proxy instance.
• properties:Array: The properties that will trigger the change event when its values change.

Returns An instance of a dispatcher that fire:

• a change event whenever any observed property changes.
• a change:NAME_OF_PROP event whenever the observed property NAME_OF_PROD changes

Example

var obj = {
  someProp: '1',
  anotherProp: 2
};

var objChange = require('object-change');

var proxyObj = objChange(obj, ['someProp']);

proxyObj.on('change:someProp', function (e, args) {
  console.log('change from: '+ args.oldValue + ' to: ' + args.newValue);
});

proxyObj.someProp = 'some other value';

// ==> output <==
// change from: 1 to: 'some other value';

proxyObj.anotherProp = 1// doesn't fire change because is not observed.

Important notes and limitations

• The events fire synchronously. So far I haven't had any problems. Make sure you don't do expensive tasks inside the change listener
• The dispatcher instance returned have the following methods:
  • on. To add a listener to an event in the dispatcher
  • fire. To fire an event on the event dispatcher
  • off. To remove the listeners The events works similarly to the jQuery on/off. fire is similar to jQuery.fn.triggerHandler
• Be aware that the properties should not be named on, fire or off
• It does not work on nested properties. This is by design, I just wanted to keep it simple.
• The base object is used as the prototype for the returned object. If you change a nested property, it will affect the original object I did it this way to avoid having to copy all the properties to the new object, but... I might consider change it in the future if it is proven to be a problem.

Changelog

Changelog