coffeescript vs javascript. rewriting http://www.spookandpuff.com/examples/dynamicTextSize.html

00_before.js

$( document ).ready( function() {
  var $body = $('body'); //Cache this for performance

  var setBodyScale = function() {
    var scaleFactor = 0.35,
    scaleSource = $body.width(),
    maxScale = 600,
    minScale = 30;

    var fontSize = scaleSource * scaleFactor; //Multiply the width of the body by the scaling factor:

    if (fontSize > maxScale) fontSize = maxScale;
    if (fontSize < minScale) fontSize = minScale; //Enforce the minimum and maximums

    $('body').css('font-size', fontSize + '%');
  }

  $(window).resize(function(){
    setBodyScale();
  });

  //Fire it when the page first loads:
  setBodyScale();
});

01_after.coffee

# based on http://www.spookandpuff.com/examples/dynamicTextSize.html

class BodyScaler
  scaleFactor: 0.35
  maxScale: 400
  minScale: 30

  constructor: ->
    @body = $("body")

  scale: =>
    scaleSource = @body.width()
    fontSize = scaleSource * @scaleFactor

    if (fontSize > @maxScale)
      fontSize = @maxScale
    if (fontSize < @minScale)
      fontSize = @minScale

    @body.css("font-size", "#{fontSize}%")

$ ->
  scaler = new BodyScaler()
  scaler.scale()
  $(window).resize(scaler.scale)

Also

$(function() {
...
});

is shorthand for

$(document).ready(function() {
...
});