In javascript how does the below code works

Question

In Javascript how does the below code works.

var a = {
  prop1: "a",
  prop2: "b",
  fun: function() {
    return this.prop1 + " " + this.prop2;
  }

}
var a2 = a;
a.fn = "v";
a = {};
if (a === a2) {
  console.log(true);
} else {
  console.log(false);
}

The above code prints false.

But if I comment out the line a={} the value which prints on console is true.

var a = {
  prop1: "a",
  prop2: "b",
  fun: function() {
    return this.prop1 + " " + this.prop2;
  }

}
var a2 = a;
a.fn = "v";
//a={};
if (a === a2) {
  console.log(true);
} else {
  console.log(false);
}

How the above code works, as Both variables(a and a2) points to the same object but when I initialized a with {} it gave false.

Answer 1

...as Both variables(a and a2) points to the same object ...

They don't anymore, as of this line:

a={};

At that point, a2 refers to the old object, and a refers to a new, different object.

a2 = a doesn't create any kind of ongoing link between the variable a2 and the variable a.

Let's throw some Unicode-art at it:

After this code runs:

var a = {
  prop1: "a",
  prop2: "b",
  fun: function() {
    return this.prop1 + " " + this.prop2;
  }

}
var a2 = a;
a.fn = "v";

At this point, you have something like this in memory (with various details omitted):

a:Ref44512−−−+
             |
             |
             |    +−−−−−−−−−−−−−+                 
             +−−−>|  (object)   |                 
             |    +−−−−−−−−−−−−−+                 
             |    | prop1: "a"  |                 
             |    | prop2: "b"  |   +−−−−−−−−−−−−+
a2:Ref44512−−+    | fun:Ref7846 |−−>| (function) |
                  | vn: "v"     |   +−−−−−−−−−−−−+
                  +−−−−−−−−−−−−−+                 

Those "Ref" values are object references. (We never actually see their values, those values are just made up nonsense.) Notice that the value in a and the value in a2 is the same, however.

If you do a === a2 at this point, it will be true: Both variables refer to the same object.

But when you do this:

a={};

                  +−−−−−−−−−−−−−+
a:Ref84521−−−−−−−>|  (object)   |
                  +−−−−−−−−−−−−−+

                  +−−−−−−−−−−−−−+                 
a2:Ref44512−−−−−−>|  (object)   |                 
                  +−−−−−−−−−−−−−+                 
                  | prop1: "a"  |                 
                  | prop2: "b"  |   +−−−−−−−−−−−−+
                  | fun:Ref7846 |−−>| (function) |
                  | vn: "v"     |   +−−−−−−−−−−−−+
                  +−−−−−−−−−−−−−+                 

At this point, a === a2 is false: The variables refer different objects.