Encapsulated object.

encapsulated.js

var obj = (function() {
  var _canvas = 'canvas';
  function _radian(x) {
    return x * Math.PI / 180;
  }

  // public api
  return {
    canvas: _canvas,
    radian: _radian
  };
})();

console.log(obj.canvas);        // canvas
console.log(obj.radian(180));   // 3.141592653589793
console.log(obj._canvas);       // undefined
console.log(obj._radian(180));  // Uncaught TypeError: Object #<Object> has no method '_radian'