How this works in JavaScript

Question

var fullname = 'John Doe';
var obj = {
   fullname: 'Colin Ihrig',
   prop: {
      fullname: 'Aurelio De Rosa',
      getFullname: function() {
         return this.fullname;
      }
   }
};

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

var test = obj.prop.getFullname;

console.log(test());

how does this code work in javascript?

Answer 1

The output of the first logging is Aurelio De Rosa and second is John Doe.
This is actually a flaw in the javascript. "this" is a reference to the current object instantiated by the class. In JavaScript, ‘this’ normally refers to the object which ‘owns’ the method, but it depends on how a function is called
When the First time obj.prop.getFullname() is logged the "this" refers to an instance of the obj but the second time when test() is logged the "this" refers to the global object. In web browser, that’s ‘window’.

Thus it's pretty clear why the o/t is such. First time this.fullname is local fullname i.e "Aurelio De Rosa" but second time this.fullname is global fullname i.e "John Doe"