radar.js

Radar.js

A simple wrapper for objects that emits events around specified methods. It effectively sandwiches object methods between two event emitters.

Installation

npm install radar.js

Quick Start

var Radar = require("./lib")
  , radar = new Radar({ methods: ["leave"] });

var bear = radar.wrap({
  name: "Bear",
  leave: function () {
    console.log(this.name + " is leaving...");
  },
  stay: function () {
    console.log(this.name + " is staying...");
  }
}, {
  prefix:  "bear",
  methods: ["stay"]
});

radar.before("bear:leave", function () {
  console.log(this.name + " is thinking about leaving...");
});

radar.after("bear:leave", function () {
  console.log(this.name + " left.");
});

radar.before("bear:stay", function () {
  console.log(this.name + " is thinking about staying...");
});

radar.after("bear:stay", function () {
  console.log(this.name + " stayed.");
});

bear.leave();
bear.stay();

// Bear is thinking about leaving...
// Bear is leaving...
// Bear is thinking about staying...
// Bear is staying...
// Bear left.
// Bear stayed.

Sync vs. Async

This library works with both synchronous and asynchronous methods, but it does require an adherence to a certain asynchronous convention -- callback parameters MUST be the last parameter supplied to a method. For example...

var okay = radar.wrap({
  asyncMethod: function (name, done) {
    done(null, name.toUpperCase());
  }
}, { prefix: "okay" });

var notOkay = radar.wrap({
  asyncMethod: function (done, name) {
    done(null, name.toUpperCase());
  }
}, { prefix: "notOkay" });

API

Radar(options) [constructor]

Create a new Radar object with some optional configuration.

Usage

var radar = new Radar();
var radar = new Radar({ methods: ["leave"] });

Arguments

name	req	type
options	n	obj

Options

name	req	type	default	description
separator	n	str	":"	separates the prefix and method name (prefix:method)
methods	n	arr	[]	list of methods to wrap, if they exist

Radar.wrap(object, options)

Wraps designated methods within an object with before and after event emitters.

Usage

var bear = radar.wrap({
  name:  "Bear",
  leave: function () {
    console.log(this.name + " is leaving...");
  }
}, { prefix: "bear" });

var fox = radar.wrap({
  name: "Fox",
  stay: function () {
    console.log(this.name + " is staying...");
  }
}, {
  prefix:    "fox",
  separator: "/"
  methods:   ["stay"]
})

Arguments

name	req	type
object	y	obj
options	y	obj

Options

name	req	type	default	description
prefix	y	str	""	prefixes the event names attached to this object
separator	n	str	":"	overrides the default separator for the object argument's events only
methods	n	arr	[]	list of additional methods to wrap for the object argument only

Radar.before(eventName, handler)

Trigger handler before the wrapped method is called on the object. The context (this) within this method is the object which the event was registered against.

Usage

radar.before("bear:leave", function () {
  console.log(this.name + " is about to leave..."); // Bear is about to leave...
});

Arguments

name	req	type
eventName	y	str
handler	y	func

Radar.after(eventName, handler)

Trigger handler after the wrapped method is called on the object. The context (this) within this method is the object which the event was registered against.

Usage

radar.after("bear:leave", function () {
  console.log(this.name + " left."); // Bear left.
});

Arguments

name	req	type
eventName	y	str
handler	y	func

License

MIT