observable-mixin

Just observe

Mixin that makes your types observable without exposing emitter.

    npm install --save observable-mixin

Usage

observable-mixin brings 1 method:

• subscribe(eventName: String, handler: Function, [once: Boolean]): Function returns a function that unsubscribes a given listener

The mixin comes as a factory function i.e. in order to get mixin it needs to invoke exported function. It is done intentionally in order to be able to pass any kind of implementation of EventEmitter.

 
    import Symbol from 'es6-symbol';
    import composeClass from 'compose-class';
    import ObservableMixin from 'observable-mixin';
    import { EventEmitter } from 'events';
 
    const FIELDS = {
        emitter: Symbol('emitter'),
        name: Symbol('name')
    };
 
    const Person = composeClass({
        mixins: [
            ObservableMixin(FIELDS.emitter)
        ],
 
        constructor(name) {
            this[FIELDS.emitter] = new EventEmitter();
            this[FIELDS.name] = name;
        },
 
        name(value) {
            if (value) {
                this[FIELDS.name] = value;
                this[FIELDS.emitter].emit('change', 'name', value);
            }
 
            return this[FIELDS.name];
        }
    });
 

import Person from './person';
 
const person = new Person('Mike Wazowski');
 
const unsubscribe = person.subscribe('change', (field, value) => {
    console.log('Person\'s', field, 'was changed to', value);
});
 
person.name('James P. Sullivan'); // Person's name was changed to 'James P. Sullivan'
 
unsubscribe();
 
person.name('Randall Boggs'); // Nothing
 

Mixin supports once subscription:

import Person from './person';
 
const person = new Person('Mike Wazowski');
 
person.subscribe('change', (field, value) => {
    console.log('Person\'s', field, 'was changed to', value);
}, true);
 
person.name('James P. Sullivan'); // Person's name was changed to 'James P. Sullivan'
 
person.name('Randall Boggs'); // Nothing