ginga

Ginga.js

Ginga is a utility module that enables a middleware based (express inspired), modular architecture for creating asynchronous JavaScript function. Supports both callback and promise.

npm install ginga

ginga([object])

Initialise ginga

var ginga = require('ginga')
var obj = ginga() //as a new object

var app = {}
ginga(app) //as a mixin

function App () { }
ginga(App.prototype) //as a prototype mixin

Method and Hook

define() and use() a method with pre, hook, invoke middleware functions. pre middlewares initiate and batch operations where invoke commits result. hook can be mounted for additional validations or amendments.

Ginga method supports both callback and promise.

app.define(name, [pre...], invoke)

app.use(name, [hook...])

var ginga = require('ginga')
var app = ginga()

// defining method
app.define('test', function (ctx, next) {
  ctx.logs = ['pre']
  next()
}, function (ctx, done) {
  ctx.logs.push('invoke')
  done(null, ctx.logs)
})

// hook
app.use('test', function (ctx, next) {
  ctx.logs.push('hook')
  next()
})

// method callback
app.test(function (err, res) {
  console.log(res) // ['pre', 'hook', 'invoke']
})

// no callback function: returns Promise
app.test().then(function (res) {
  console.log(res) // ['pre', 'hook', 'invoke']
})

Middleware

Middleware turns asynchronous function into encapsulated, reusable set of building blocks.

Upon calling a method, Ginga goes through a sequence of functions middleware. A middleware consists of arguments:

• ctx - context event emitter object. Emits .on('end', fn) event on callback with error and result arguments.
• next - callback function, invoke with next() or next(err, result) or asyncFn(next(resolveFn))

The context object ctx maintains state throughout the method call, while encapsulated from this object.

A middleware can make changes to context object, or access changes made by previous middleware functions.

Given next argument, current middleware must call next() to pass control to the next middleware, or next(err, result) to end the sequence and callback with error or result. Otherwise the method will be left hanging.

ginga.params([param...])

Ginga built in ginga.params middleware for parsing method arguments. Supports optional parameters and type-checking. param is a string in form

name[:type][?]

• name - name of parameter mapped from argument
• type type checking (optional): string, boolean, function, number, date, regexp, object, array, case insensitive.
• ? - optional parameter.

var ginga = require('ginga')
var params = ginga.params

var app = ginga()

//define method with params parsing
app.define('test', params('a', 'b:number?', 'c:string?'), function (ctx, done) {
  done(null, ctx.params) 
})

//call method
app.test('s', 1, function (err, res) {
  console.log(res) //{ a: 's', b: 1 }
})
app.test('s', 't', function (err, res) {
  console.log(res) //{ a: 's', c: 't' }
})
app.test(function (err, res) {
  console.log(err) //Error: Too few arguments. Expected at least 1
})

Plugin

app.use(plugin)

app.use also accepts Ginga object as plugin. This will mount hooks into the main app.

var ginga = require('ginga')

//define app
var app = ginga() 
app.define('test', function (ctx, next) {
  ctx.logs = ['pre']
  next()
}, function (ctx, done) {
  ctx.logs.push('invoke')
  done(null, ctx.logs)
})

//define plugin
var plugin = ginga()
plugin.use('test', function (ctx, next) {
  ctx.logs.push('plugin')
  next()
})

//use plugin
app.use(plugin)

//call methods
app.test(function (err, res) {
  console.log(res) //['pre','plugin', 'invoke']
})

Inheritance

By initialising Ginga with prototype mixin, hooks are also inherited in prototype chain:

var ginga = require('ginga')

function App () { }
var A = ginga(App.prototype) //ginga prototype mixin

A.define('test', function (ctx, next) {
  ctx.logs = ['pre']
  next()
}, function (ctx, done) {
  ctx.logs.push('invoke')
  done(null, ctx.logs)
})

var a1 = new App()
var a2 = new App()

//prototype hook
A.use('test', function (ctx, next) {
  ctx.logs.push('A hook')
  next()
})

//instance hook
a1.use('test', function (ctx, next) {
  ctx.logs.push('a1 hook')
  next()
})
a2.use('test', function (ctx, next) {
  ctx.logs.push('a2 hook')
  next()
})

//call methods
a1.test(function (err, res) {
  console.log(res) //['pre','A hook','a1 hook', 'invoke']
})
a2.test(function (err, res) {
  console.log(res) //['pre','A hook','a2 hook', 'invoke']
})

License

MIT