mixin-util

A mixin utility for ES2015 Classes

Basic usage

The function accepts the names of mixins or mixin fnctions

const mixinUtil = require('mixin-util');

class MyCoolClass extends mixinUtil('settings', 'middleware') {
  constructor() {
    // nothing will work if super is not called
    super();
  }
}

let mcc = new MyCoolClass();

mcc.set('test', 'works');

// log -> works
console.log(mcc.get('test'));

Mixins

Middleware

this mixin adds middleware functionality similar to that of express.

.use

This method will add functions to the middleware stack. Any arrays passed will be flattened. For eaxmple,

.use(function () {}, [function () {}, function () {}]);

... is the same as...

.use(function () {}, function () {}, function () {});

Error handling middleware ware should accept and error, the expected arguments, and then next. To forward and error to the error handler simply pass it to the next function or throw the error.

.handle

This method will exacute the middleware stack. It accepts the arguments to be passed to the middle functions.

Example:

const mixinUtil = require('mixinUtil');

class MyMiddleware extends mixinUtil('middleware') {
  constructor() {
    super();
  }
}

let middle = new MyMiddleware();

middle.use(function (err, icecream, next) {
  // called because of bacon
  // log -> eww bacon icecream
  console.log(err);
});

middle.use(function (icecream, next) {
  icecream.add('cherry');
  next();
});

middle.use(function (icecream, next) {
  icecream.add('bacon');
  next();
});

middle.use(function (icecream, next) {
  if(icecream.is('bacon'))
  next(new Error("eww bacon icecream"));

  // next can only be called once so this is ok
  next();
});

// call stack
middle.handle(icecream);

Settings

This mixin adds setting functionality. For Each of these methods the instance methods applies to the instance and the static method applies to the prototype.

.set

This method accepts the name of the setting and the new value

.set('test', 'works')

.get

This method accepts the name of the setting and returns the value of that setting

.get('test')
// returns 'works'

.Setter

This method will assign a setter to a setting. The setter function should accept a value and return the transformed value.

.Setter('name', function uppercase(name) {
  return name.toUpperCase();
});

.Getter

This method will assign a getter to a setting. You can think of a getter as a imaginary setting. The getter function should accept a object containing all of the settings.

// Settings -> {
//   name: {
//     first: 'john',
//     last: 'doe',
//   }
// }

.Getter('name.full', function fullname(settings) {
  return `${settings.name.first} ${settings.name.last}`;
});

Mixin Pattern

function myMixin(parentClass) {
  // private variables
  let _private = Symbol("private");

  class MyMixin extends parentClass{
    constructor() {
      super();
      this[_private] = "hi";
    }
  }

  return MyMixin
}

License

MIT