// In browsers _this is set to window in the global scope
console.log(this === window);

(function(){
  console.log(this === window)

  var myAwesomeFunction = function(name, age){
    // This will be whatever you want it to be
    console.log(this, name, age);
  };

  myAwesomeFunction.call({a: 10}, 'Ruby', 100);
  // BTW: use apply if you want to pass in an array of arguments
  myAwesomeFunction.apply({a: 10}, ['Ruby', 200]);

  /**
   * @param {String} name
   * @param {Number} age
   *
   * @constructor
   */
  var Person = function Person(name, age) {
    /**
     *
     * @type {String}
     */
    this.name = name;

    /**
     *
     * @type {Number}
     */
    this.age = age;

    // JS will automatically set this for constructors ...
    console.log(this);
  };

  Person.prototype.sayHi = function() {
    // ... or for methods
    console.log(this);
  };

  var me = new Person('Ruby', 300);
  me.sayHi();
})();