In prototype chain method calls, this refers to the instance object that the method is called on, not the prototype object where the method is defined.
When you call a method defined on a prototype (e.g., instance.method()), the this inside the method refers to the instance object, regardless of where the method resides in the prototype chain. This is because the method is invoked as a property of the instance, even if the property is inherited. Example: function Person(name) { this.name = name; } Person.prototype.greet = function() { console.log(this.name); }; const alice = new Person('Alice'); alice.greet(); // 'Alice' (this refers to alice instance, not Person.prototype).