Exert

Exert is a very simple library that allows to create watchables. Watchables are subscribable classes in which you can control publish timings.

It works by taking advantage of ES next decorators.

Installation

npm install exert

You will also want to setup your project to support class and object decorators. See: https://babeljs.io/docs/plugins/transform-decorators/

How it works

Create a watchable class.

import { watchable, change, changeAsync } from 'exert';

@watchable()
class MyWatchable {
  constructor() {
    this.firstName = 'Scott';
  }

  // @change decorator will automatically notify all subscriptions after
  // changes are made.  Works with synchronous methods.
  @change setName(firstName) {
    this.firstName = firstName;
  }

  // @changeAync will pass the "done" function as the last argument.
  // Use with async methods such as calling a backend REST call.
  @changeAsync setNameAsync(firstName, done) {
     window.setTimeout(()=> {
       this.firstName = firstName;
       done();
     }, 1000);
  }
}

In the above, we use @change and @changeAsync decorators to publish out to subscribers. Generally any changes to public properties should be changed via a method decorated with @change or @changeAsync so that subscribers are correctly called.

Now that we have setup our class, we are ready to instantiate it and start subscribing/watching the class.

let myWatchable = new MyWatchable();

let onUpdate = (current, prev)=> {
  console.log('name was:' + prev.firstName);
  console.log('name is now:' + current.firstName);
  // Do whatever you want.
  // Typically, you may want to update/render the view.
}

// Subscribe to the stream updates. This will fire the next time a change is
// made.
myWatchable.watch(onUpdate);

// Subscribe and immediately calls onUpdate.
myWatchable.watchNow(onUpdate);

// Make a change.
myWatchable.setName('John'); // You should see onUpdate called.

// Unsubscribe.
myWatchable.unwatch(onUpdate);

// Subscribe Once
myWatchable.watchOnce(onUpdate);

// Make async change
myWatchable.setNameAsync('Michael');  // You should see onUpdate called again.

Contribute

Installation

npm install

Scripts

• yarn build or npm run build - General lib files.
• yarn dev or npm run dev - Produce dev version of lib and watch files.
• yarn test or npm run test - Run tests
• yarn test:watch or npm run test:watch - Run tests and watch.

To publish: npm publish