Question

Code is from mozilla website

function Product(name, price) {
  this.name = name;
  this.price = price;

  if (price < 0)
    throw RangeError('Cannot create product "' + name + '" with a negative price');
  return this;
}

function Food(name, price) {
   Product.call(this, name, price);/// why not this be Product(name,price)
   this.category = 'food';
}
Food.prototype = new Product();

may very silly thing, can’t understand this line
Product.call(this, name, price);

Since both Product and Food are global functions why do we have to use Product.call

Answer 1

Because you want to apply the Product function on the food object. Just invoking it without call would lead to a wrong this value, and the properties added in Product would be attached to the wrong object.

Also learn here about inheritance.