modification
v1.0.0
Published
Process changes that should be made on the prototype and emit `change` event for each changed property
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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