modification

Modification is a small helper function that helps you process changes on the prototype of your instances as it will automatically emit change events for properties that you've changed.

Installation

This module is intended for server and client usage and is released in the public npm repository and can be installed using:

npm install --save modification

Usage

In all of the examples we're going to assume the following setup:

'use strict';
 
var modification = require('modification')
  , EventEmitter = require('events').EventEmitter;
 
function Foo() {
  this.bar = 'baz';
  this.foo = 'bar';
 
  EventEmitter.call(this);
}
 
require('util').inherits(Foo, EventEmitter);

The modification module exports function that returns another function upon invocation. The modification function can called with 1 option argument which specifies the suffix of the event that needs to be emitted:

Foo.prototype.change = modification(' changed');

In the example above we will automatically emit foo changed once we change the foo property through the set .change method:

var foo = new Foo();
 
console.log(foo.foo); // 'bar';
 
foo.on('foo changed', function (currently, previously) {
  console.log(this.foo);    // hi
  console.log(currently);   // hi
  console.log(previously);  // bar
});
 
foo.change({ foo: 'hi' });

As you can see in the example above we need to pass an object with the changes for the prototype. If one of the properties in the supplied object does not exist on the foo instance we will ignore it. If it does exist but is the same we will not emit the event or change the value. If it has a different value we will emit: <name of the property><supplied suffix> with the current value and the previous value.

The introduced .change method will this so it can be used for chaining.

License

MIT