Why Commenting/uncommenting Alert() In Constructor Toggles Variable As Part Of The Obj Instances

In the following code, if I comment //alert('Your Name is: ' +fname); in the constructor function then 'alert(p1.fname);alerts 'Suresh' and If I remove the comment out thealert('Yo

Solution 1:

You're using a variable that doesn't exist in the first alert(), so get you an error message telling you the variable is not defined`

There is no variable named fname inside the person() function, it's called this.fname, just like you created it

function person () {
    this.fname = "Suresh";
    alert("Your Name is: " + this.fname);
  }

  var p1 = new person();

  alert(p1.fname);

FIDDLE