如何计算项目数组中的总价格

Question

我是js的新手，在一个网上商店有一个购物车，我正在做一个Javascript的任务，我不能得到我的总价工作，当用户点击项目添加到购物车时显示在网页上。这是我的项目数组，任何帮助将不胜感激，谢谢你

var cart;
var items = new Array(); //create array to store items
items[0] = "Greatest Hits CD", 10;
items[1] = "Girls CD", 10;
items[2] = "Shirt1", 20;
items[3] = "Mask Tee", 20;
items[4] = "Crewneck", 25;
items[5] = "Tour Poster", 9;

这是我的显示函数

this.display = function () {  
this.holder.innerHTML = "";  
this.totalprice = 0; 
for (var i=0; i<this.quantities.length; i++) {  
if (this.quantities[i] > 0) {  
this.totalprice += this.quantities[i]*this.items[i]; 
var elm = document.createElement('div');  
elm.innerHTML = "<span class='name'>"+this.items[i]+" </span><span class='quantity'>Quantity: "+this.quantities[i]+"</span>";  
this.holder.insertBefore(elm, null);  
    }  
} 
var elm = document.createElement('div');  
elm.innerHTML = "<span class='price'>Total Price: $"+this.totalprice+" </span>"; 
this.holder.insertBefore(elm, null);  
document.getElementById('quantities').value = cart.quantities; 
document.getElementById('items').value = cart.items; 
    }

Answer 1

Array Reduce方法非常适合于此，特别是与Array destruct结合使用时，因为我们只关心价格:

var items = [ 
    ["Greatest Hits CD", 10],
    ["Girls CD"        , 10],
    ["Shirt1"          , 20],
    ["Mask Tee"        , 20],
    ["Crewneck"        , 25],
    ["Tour Poster"      , 9]
];
console.log(
    items.reduce((total, [,price]) => total + price, 0)
);

Answer 2

您正在尝试创建一个关联数组(键/值对)，这不是JavaScript中标准数组的工作方式。

相反，创建一个存储数据的对象数组。每个"记录"将被持久化为一个对象，这些对象将获得一组公共属性名称(在我的示例中是prop1和prop2)。然后，您可以循环遍历对象数组，并在每次迭代中获取您感兴趣的属性(在本例中为prop2)。

var items = new Array(); //create array to store items
// Each item in the array will store an object with 2 properties
// Object literal syntax: {propertyName : propertyValue, propertyName : propertyValue, etc.}
items[0] = {prop1:"Greatest Hits CD", prop2:10};
items[1] = {prop1:"Girls CD", prop2:10};
items[2] = {prop1:"Shirt1", prop2:20};
items[3] = {prop1:"Mask Tee", prop2:20};
items[4] = {prop1:"Crewneck", prop2:25};
items[5] = {prop1:"Tour Poster", prop2:9};
var sum = null;   // Place to store the total cost
  
// The JavaScript Array.prototype specifies a built-in method called
// forEach that takes a function as an argument. That function is
// automatically passed 3 arguments and is executed for each element 
// in the array.
items.forEach(function(value, index, arry){
 sum += value.prop2;
});
console.log(sum);