shared.js

A factory for a passive mediator design pattern in <20 lines of Javascript

Use case:

The motivation of this project was to easily share state amongst React Native components allowing for lose coupling between them. This allows a component to update the state and the others to see the update, and is a light weight alternative to using an event emitter since it does not use callbacks. Rather it is up to the Observers to check the state changes.

Installation

Use npm install shared.js --save

Example

A use case could include a button that needs to check the state of multiple on/off switches before proceeding. Rather than coupling the switches to the button, a shared object can be used by the switches to change state,and the button to perform a check when it is pressed.

var Share = require('shared.js');
var id = 'buttonTest';
Share.getShare(id).canProceed = function() {

  for (var internal in this) {
    if (internal.indexOf('toggle') !== -1) {
      if (!this[internal]) {
        return false;
      }
    }
  }
  return true;
};

Share.getShare(id).switch = function() {
  Share.getShare(id)[this.name] ?
    Share.getShare(id)[this.name] = false : Share.getShare(id)[this.name] = true;
};
var toggle1 = {
  name: 'toggle1',
  share: Share.getShare(id, 'toggle1', false),
  toggle: Share.getShare(id).switch
};


var toggle2 = {
  name: 'toggle2',
  share: Share.getShare(id, 'toggle2', false),
  toggle: Share.getShare(id).switch
};

var button = {
  share: Share.getShare(id),
  press: function() {
    return this.share.canProceed();
  }
};

console.log(button.press());// false
toggle1.toggle();
console.log(button.press());// false
toggle2.toggle();
console.log(button.press());// true

// lets add a new toggle
var toggle3 = {
  name: 'toggle3',
  share: Share.getShare(id, 'toggle3', false),
  toggle: Share.getShare(id).switch
};
console.log(button.press()); // false
toggle3.toggle();
console.log(button.press());// true

Functions

• getShare (id, property, initialValue) - retrieve a shared state object as identified by the id argument. All arguments are optional and if none are passed the function returns a default system-wide share object. The same system-wide object is returned when getShare is called without arguments.

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MIT Licenced