The code example of this keyword in Javascript

  var fullname = 'David';
    var obj = {
       fullname: 'john mars',
       prop: {
          fullname: 'Brett',
          getFullname: function() {
             return this.fullname;
          }
       }
    };

    console.log(obj.prop.getFullname());

    var testing = obj.prop.getFullname;

    console.log(test());

The example code written above will print Brett and David. The reason behind this is that the context of a function defined above (context refers to the global object). In JavaScript , it depends on how a function is invoked.

In the above code- console.log() call, getFullname() is defined as the function of the ( obj.prop ) object. So, the function defined above will returns the fullname property of this object.

getFullname() is assigned to the testing variable so context refers to the global object .

For this reason, the function returns the value of a property called fullname of window.