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Prototype Javascript-2

rwniceing asked
Last Modified: 2014-08-25
Dear Experts,

I have set up cook menu price calculation function for two customers, Bob and John to pay after ordering food and drink. It is easy using function, and now the owner restaurant changes the price formula by using the prototype, now the new price is changing to replace the old price formula so they need to pay new price.

But the console.log("Bob pay new price:", guest_Bob_price.price(2,3)); is not working
because  prototype property "price" is conflict to  this.price in the function. It will
be solved if using  prototype pricechg property to replace price property . I want use the same price  property before and after the formula change. How to do it on javascript prototype ?
The following code is not working at the console.log("Bob pay new price:", guest_Bob_price.price(2,3));

please advise


<!DOCTYPE html>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<script type="text/javascript">

function CookMenu(food,drink){
	if (CookMenu.prototype.pricechg==undefined){
    return this;
function start(){
var guest_Bob_price = new CookMenu(2,3);
var guest_John_price = new CookMenu(5,6);

console.log("Bob pay old price:", guest_Bob_price.price);
console.log("John pay old price:", guest_John_price.price);

//-Menu price might change if input value=1
if (document.getElementById("owner").value==1){
CookMenu.prototype={price:function(food,drink){ return 300*food+700*drink; }};
var owner_restaurant=new CookMenu(2,3);

var guest_Bob_price = new CookMenu(2,3);
var guest_John_price = new CookMenu(2,3);
console.log("Bob pay new price:", guest_Bob_price.price(2,3));
console.log("John pay new price:", guest_John_price.price(2,3));

<body onload="start();">
Prototype javascript tutorial, for example, restaurant menu price change
<input type="text" name="owner" id="owner" value="1" />

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