Fat Arrows and Classes-as-Prototype-sugar make a beautiful future for JavaScript

device.js

var stream = require("fake-stream-lib"),
    Emitter = require("events").EventEmitter,
    util = require("util");


// Today...

function Device( opts ) {

  this.value = null;

  // open an async stream,
  // this will be called continuously
  stream.read( opts.path, function( data ) {

    // Update this instance's current value
    // with the most recent value from the
    // data stream
    this.value = data;

  }.bind(this) );

  // Throttle the frequency of events emitted from
  // this Device instance
  setInterval(function() {

    // Emit a throttled event
    this.emit("event");

  }.bind(this), opts.freq || 100 );
}

util.inherits( Device, Emitter );

Device.prototype.scale = function( low, high ) {
  return this.value * ( high - low ) / 1023 + low;
};


// ------------------------------------------------------ //

// w/ Fat Arrow...

function Device( opts ) {

  this.value = null;

  // open an async stream,
  // this will be called continuously
  stream.read( opts.path, data => {

    // Update this instance's current value
    // with the most recent value from the
    // data stream
    this.value = data;

  });

  // Throttle the frequency of events emitted from
  // this Device instance
  setInterval(() => {

    // Emit a throttled event
    this.emit("event");

  }, opts.freq || 100 );
}

util.inherits( Device, Emitter );

Device.prototype.scale = function( low, high ) {
  return this.value * ( high - low ) / 1023 + low;
};



// ------------------------------------------------------ //

// w/ Fat Arrow & Class...


class Device extends Emitter {

  constructor( opts ) {

    super();

    this.value = null;

    // This example uses the expression
    // form of a fat arrow
    stream.read( path, data => this.value = data );

    // Throttle the frequency of events emitted from
    // this Device instance
    setInterval(() => {

      // Emit a throttled event
      this.emit("event");

    }, opts.freq || 100 );
  }

  scale( low, high ) {
    return this.value * ( high - low ) / 1023 + low;
  }
}

// ------------------------------------------------------ //

// w/ Fat Arrow, Class & Destructuring with default parameter values...

class Device extends Emitter {

  constructor({ path, freq = 100 }) {

    super();

    this.value = null;

    // This example uses the expression
    // form of a fat arrow
    stream.read( path, data => this.value = data );

    // Throttle the frequency of events emitted from
    // this Device instance
    setInterval(() => {

      // Emit a throttled event
      this.emit("event");

    }, freq );
  }

  scale( low, high ) {
    return this.value * ( high - low ) / 1023 + low;
  }
}

VERY COOL!

The only part that isn't covered in the ES wiki is how destructuring of an object parameter works with default values :(

I just asked @allenwb and updated the gist. It allows the use of = in the object parameter.