未捕获的TypeError：无法读取未定义的属性“数量”

Question

I have a function

var foodArray = [] // this global variable arr contains list of object with property 'name' and 'quantity'. 

function x (){
 $('#menu-list button').click(function(){
//judge whether a button is add or minus
var type = $(this).attr('name');
//find current minus button element
var minus = $(this).closest('.food-edit').find('.minus');
//find current item's sales number element
var nSales = $(this).closest('.food-edit').find('.num-sales');
//conver current item's sales to a number
var num_Sales = Number(nSales.text());

//find food attributes
var foodNameStr = $($(this).closest('.food-detail').find('.food-name')).text();
var foodPrice = $($(this).closest('.food-detail').find('.food-price-num')).text();
var foodPrice_Num = parseFloat(foodPrice);

//take a food ID in DB
var foodID = $(this).closest('.food-detail').attr('id');
var getIndex = FindIt(foodID,foodArray);



if (type == "add") { //add a food into basket
    minus.show();
    TotalOperation(type,foodPrice_Num);
    if ( getIndex == -1) {
        var foodObj = {};
        //add a new object
        foodObj.ID = foodID;
        foodObj.name = foodNameStr;
        foodObj.price = foodPrice_Num;
        foodObj.quantity = 1;
        foodArray.push(foodObj);
        nSales.text("1");
    }
    else {
        EditQuantity(nSales,getIndex);// I get a index from previous code and pass to this function.And before I call this function. The arr already has couple objects for sure.
    }


}

}

function EditQuantity(ns,index){
  arr[index].quantity++;
  ....
}

When the execute to EditQuantity, it gives me a error Uncaught TypeError: Cannot read property 'quantity' of undefined. But If I put arr[index].quantity++; directly in the function x, it works fine. When it goes to a helper function it gives such error. What do I did wrong?

Answer 1

1. Replace 'arr' with global array 'foodarray' in function 'EditQuantity'.
2. Currently, the elements are added to foodArray only if getindex = -1 which is incorrect. This will always results in foodArray never having more than 1 element.

To fix it, in place of 'else' use if (getindex!=-1) before calling EditQuantity method.