在javascript中从对象获取价值

Question

我有几个对象作为这个结构：

然后我创建一个函数来更新与搜索ID匹配的项目数量：

function setQuantityInCartByID(json, itemID, val){
    for(var i in json){
        console.log(json[i].ID);
        if(json[i].ID == itemID){
           json[i].QuantityInCart = val;
           break;
        }
     }
     return json;
}

这是我的JSON;

{"DepartmentID":12,"CategoryID":117,"BrandID":19,"BrandImage":"         ","BrandName":"General","ID":708,"Name":"Grand 6Port Power Center","PictureName":"http://111.92.241.110/wwwProducts/unknown.PNG","Notes":"","PriceShow":"$10.00","Price":0,"PriceA":0,"PriceB":0,"PriceC":0,"WebsitePrice":0,"Quantity":2,"QuantityInCart":2,"LastUpdated":"/Date(1378108144050)/","Active":1,"PriceLevel":0,"NewProductImage":"http://111.92.241.110/wwwProducts/newproduct.png","isNewProduct":false,"isInStock":"10 Available in Stock(s)!","NewArrival":0,"ExpireNewArrival":"/Date(-62135596800000)/","NewPromotion":0,"ExpireNewPromotion":"/Date(-62135596800000)/"}

{"DepartmentID":12,"CategoryID":117,"BrandID":19,"BrandImage":"         ","BrandName":"General","ID":709,"Name":"Grand 6Port Power Center","PictureName":"http://111.92.241.110/wwwProducts/unknown.PNG","Notes":"","PriceShow":"$10.00","Price":0,"PriceA":0,"PriceB":0,"PriceC":0,"WebsitePrice":0,"Quantity":2,"QuantityInCart":2,"LastUpdated":"/Date(1378108144050)/","Active":1,"PriceLevel":0,"NewProductImage":"http://111.92.241.110/wwwProducts/newproduct.png","isNewProduct":false,"isInStock":"10 Available in Stock(s)!","NewArrival":0,"ExpireNewArrival":"/Date(-62135596800000)/","NewPromotion":0,"ExpireNewPromotion":"/Date(-62135596800000)/"}       

{"DepartmentID":12,"CategoryID":117,"BrandID":19,"BrandImage":"         ","BrandName":"General","ID":710,"Name":"Grand 6Port Power Center","PictureName":"http://111.92.241.110/wwwProducts/unknown.PNG","Notes":"","PriceShow":"$10.00","Price":0,"PriceA":0,"PriceB":0,"PriceC":0,"WebsitePrice":0,"Quantity":2,"QuantityInCart":2,"LastUpdated":"/Date(1378108144050)/","Active":1,"PriceLevel":0,"NewProductImage":"http://111.92.241.110/wwwProducts/newproduct.png","isNewProduct":false,"isInStock":"10 Available in Stock(s)!","NewArrival":0,"ExpireNewArrival":"/Date(-62135596800000)/","NewPromotion":0,"ExpireNewPromotion":"/Date(-62135596800000)/"}

问题：console.log(json[i].ID);结果未定义。

Answer 1

我认为你不需要for循环。看起来你的参数json已经是一个对象，所以不需要循环，只需去json.ID

Answer 2

您可以直接访问属性，如下所示：

if (json.ID == itemID) {
    json.QuantityInCart = val;
}

Answer 3

之前的链接似乎并不适用于我做了一个小提琴来测试它。我还更新了第一个例子。

http://jsfiddle.net/AFZhT/

这也假设您已完成类似var json = JSON.parse(data)

的操作

如果返回一个对象数组，则您的数据应类似于以下内容。这将作为json参数传递到setQuantityInCartByID函数：

var json = [{"DepartmentID":12,"CategoryID":117,"BrandID":19,"BrandImage":"         ","BrandName":"General","ID":708,"Name":"Grand 6Port Power Center","PictureName":"http://111.92.241.110/wwwProducts/unknown.PNG","Notes":"","PriceShow":"$10.00","Price":0,"PriceA":0,"PriceB":0,"PriceC":0,"WebsitePrice":0,"Quantity":2,"QuantityInCart":2,"LastUpdated":"/Date(1378108144050)/","Active":1,"PriceLevel":0,"NewProductImage":"http://111.92.241.110/wwwProducts/newproduct.png","isNewProduct":false,"isInStock":"10 Available in Stock(s)!","NewArrival":0,"ExpireNewArrival":"/Date(-62135596800000)/","NewPromotion":0,"ExpireNewPromotion":"/Date(-62135596800000)/"},

    {"DepartmentID":12,"CategoryID":117,"BrandID":19,"BrandImage":"         ","BrandName":"General","ID":709,"Name":"Grand 6Port Power Center","PictureName":"http://111.92.241.110/wwwProducts/unknown.PNG","Notes":"","PriceShow":"$10.00","Price":0,"PriceA":0,"PriceB":0,"PriceC":0,"WebsitePrice":0,"Quantity":2,"QuantityInCart":2,"LastUpdated":"/Date(1378108144050)/","Active":1,"PriceLevel":0,"NewProductImage":"http://111.92.241.110/wwwProducts/newproduct.png","isNewProduct":false,"isInStock":"10 Available in Stock(s)!","NewArrival":0,"ExpireNewArrival":"/Date(-62135596800000)/","NewPromotion":0,"ExpireNewPromotion":"/Date(-62135596800000)/"} ,      

    {"DepartmentID":12,"CategoryID":117,"BrandID":19,"BrandImage":"         ","BrandName":"General","ID":710,"Name":"Grand 6Port Power Center","PictureName":"http://111.92.241.110/wwwProducts/unknown.PNG","Notes":"","PriceShow":"$10.00","Price":0,"PriceA":0,"PriceB":0,"PriceC":0,"WebsitePrice":0,"Quantity":2,"QuantityInCart":2,"LastUpdated":"/Date(1378108144050)/","Active":1,"PriceLevel":0,"NewProductImage":"http://111.92.241.110/wwwProducts/newproduct.png","isNewProduct":false,"isInStock":"10 Available in Stock(s)!","NewArrival":0,"ExpireNewArrival":"/Date(-62135596800000)/","NewPromotion":0,"ExpireNewPromotion":"/Date(-62135596800000)/"}];

在你的页面中，以下内容将从上面接收json对象，现在它应该有一个长度。

function setQuantityInCartByID(json, itemID, val){
 for(var i in json){
        console.log(json[i].ID);
        if(json[i].ID == itemID){
           json[i].QuantityInCart = val;
           break;
        }
     }
     return json;
}

以下是您似乎一直在考虑的旧方式：

function setQuantityInCartByID(json, itemID, val){
    for(var i = 0; i <json.length;i++)
    {
        console.log(json[i].ID);
        if(json[i].ID === itemID){
           json[i].QuantityInCart = val;
           break;
        }
     }
     return json;
}

Answer 4

你所拥有的是一个javascript对象，而不是一个数组，并且你正在处理属性而不是指标。

我认为您要完成的是在不知道名称的情况下访问对象的属性。要做到这一点，你可以使用for ... in循环：

for(key in data) {
    if(data.hasOwnProperty(key)) {
        var value = data[key];
        //do something with value;
    }
}

如果你想使用简单的javascript，那么你可以使用上面的代码。