Javascript constructor and prototype issue

Question

I have the following code which I am confused why when I define a prototype of property 'name' it comes out as '40' and not 'fred'? what is going on inside javascript? this seems like a simple question but one that I am confused about. Thanks!

function Product(id){
    this.id = id
    this.name = id + 20
}

Product.prototype.name = 'fred';
var p = new Product(20);
console.log(p.name);

Answer 1

Because you did this.name = id + 20 .

p.name will find the name property in the instance first, if not found, then try to find in the prototype.

function Product(id){
    this.id = id
}

Product.prototype.name = 'fred';
var p = new Product(20);
console.log(p.name); // then it will be fred