javascript - 检查 JSON 中是否存在子数组

Question

这是 json 示例:

    {
   "kind": "shopping#product",
   "id": "tag:google.com,2010:shopping/products/6582229/17914968800165668776",
   "selfLink": "https://www.googleapis.com/shopping/search/v1/public/products/6582229/gid/17914968800165668776?alt\u003djson",
   "product": {
    "googleId": "17914968800165668776",
    "author": {
     "name": "Red Tag Market",
     "accountId": "6582229"
    },
    "creationTime": "2010-11-30T10:00:00.000Z",
    "modificationTime": "2011-05-01T09:20:00.000Z",
    "country": "US",
    "language": "en",
    "title": "The Fantastic Mr. Fox - BLU-RAY/DVD",
    "description": "Wit.",
    "link": "ht361",
    "condition": "new",
    "gtin": "00024543657552",
    "inventories": [
     {
      "channel": "online",
      "price": 22.51,
      "currency": "USD"
     }
    ],
    "images": [
     {
      "link": "http://208.131.143.232/i/6/3/0/7/6/1/8.jpg",
      "thumbnails": [
       {
        "width": 60,
        "height": 60,
        "link": "hBEevU46OsArJElwIeErF_3E7Zzu12M2eLSvQBdYiMLaRWrI60aF8lHxRqOz-wkx2YJUIVdCrzrEQDWxgcc"
       }
      ]
     }
    ]
   }
  },
  {
   "kind": "shopping#product",
   "id": "tag:google.com,2010:shopping/products/6296724/17894083551590155418",
   "selfLink": "https://www.googleapis.com/shopping/search/v1/public/products/6296724/gid/17894083551590155418?alt\u003djson",
   "product": {
    "googleId": "17894083551590155418",
    "author": {
     "name": "eBay",
     "accountId": "6296724"
    },
    "creationTime": "2011-04-04T00:43:02.000Z",
    "modificationTime": "2011-04-04T00:43:02.000Z",
    "country": "US",
    "language": "en",
    "title": "Fy.",
    "link": "htt530831212&itemid\u003d140530831212&icep_meta_categ_id\u003d11232",
    "condition": "used",
    "gtin": "00024543657552",
    "inventories": [
     {
      "channel": "online",
      "price": 14.99,
      "currency": "USD"
     }
    ],
    "images": [
     {
      "link": "http://i.ebayimg.com/00/%24%28KGrHqYOKkQE1r4Vh1gFBNl4n0t17g%7E%7E_1.JPG?set_id\u003d8800005007",
      "thumbnails": [
       {
        "width": 60,
        "height": 60,
        "link": "http://lh
       }
      ]
     }
    ]
   }
  }

我想做的是查看 data.items[i].product.images[] 是否存在。正如您所看到的，第二个响应中没有出现 Images 数组，因此当我尝试将 data.items[i].product.images[] 用于任何目的时，我的 JavaScript 就被终止了。我一直在寻找，但尚未找到解决方案。

编辑:我刚刚尝试过，但仍然没有骰子:

if(data.items[i].product.images !== undefined){
    var image = 'images/inverticon.png';
}else{
    var image = data.items[i].product.images[0].thumbnails[0].link;
}

我没有收到任何错误，脚本只是停止运行。如果我省略图像代码，一切都会正常工作，只要返回的 JSON 具有 image[]，它就可以正常工作。

编辑: 这是解决方案:

if(data.items[i].product.images !== undefined){
    var image = data.items[i].product.images[0].thumbnails[0].link;
}else{
    var image = 'images/inverticon.png';
}

Answer 1

if (data.items[i].product.images !== undefined) {
  //do what you will
}

尝试访问不存在的对象的属性将返回未定义。这很可能是您遇到的错误？

您了解网络浏览器中的网络检查器工具吗？它们都有一个控制台，任何错误都会输出到该控制台。如果你检查一下，你就会发现哪里出了问题。

您仍在尝试在该条件语句的 else 中访问图像数组，这将导致错误。

应该是这样的

if(data.items[i].product.images !== undefined){
  var image = data.items[i].product.images[0].thumbnails[0].link;

} else {
  var image = 'images/inverticon.png';
}

“不等于未定义”相当于说“已定义”