You can check the given property is an own property of an object. You can use the hasOwnProperty()
of the object
function Product(name){ this.name=name } Product.prototype.price=1 Product.prototype.getDiscount=function(){ return this.price*5/100 } var product= new Product('Fanta') console.log("name is a property of product "+product.hasOwnProperty("name")) console.log("price is a property of product "+product.hasOwnProperty("price"))
You can have the following output
>name is a property of product true
>price is a property of product false