SOURCE

function Product(name){
    this.name = name || 'apple'
    this.price = function(){
        this.name + '18'
    }
}
Product.prototype.size = function(a){
    console.log(this.name + a)
}
function subProduct(name){
    Product.call(this)
    this.name = name || 'tom'
}
subProduct.prototype = new Product()

var b = new subProduct()
console.log(b.name)
console.log(b.size(123))

//函数可复用,可传参,可继承实例属性和方法也可继承原型实例属性和方法