basic example of this object

simple_this_ex.js

var a, b, c, d, e;

a = function(obj) {
  return this; 
}


// when you call the function in 'function form' 'this' is window object
  
  a(); // window

// Always! Even if you define and call it inside another function

  (function() {
    var aa = a;
    var bb = aa();
    return bb; // window
  })();


// when you call it as a method of some object 'this' will be that object
  
  b = { a : a }; 
  b.a(); // b object


// when you use the function as a constructor with 'new' operator new 
// object will be created inside, assigned to 'this' and then returned
  
  c = new a(); // object a - instance of the a constructor function


// when you use the function as a callback for some events on DOM element
// it will be the context of the function

  d = document.getElementById('myDiv');
  d.addEventListener('click', a, false); // HTMLDivElement