Javascript 检查JSON中是否没有数组

我有一个用于获取结果的API。当它得到结果时，我会得到类似这样的结果：

{"currentPage":1,"numberOfPages":1,"totalResults":1,"data":[{"id":"Sf8xxo","name":"The Bear Reader Huckleberry Oatmeal Stout","nameDisplay":"The Bear Reader Huckleberry Oatmeal Stout","abv":"6.3","ibu":"33","styleId":21,"isOrganic":"N","status":"verified","statusDisplay":"Verified","createDate":"2015-03-22 17:35:03","updateDate":"2015-03-22 17:35:03","style":{"id":21,"categoryId":1,"category":{"id":1,"name":"British Origin Ales","createDate":"2012-03-21 20:06:45"},"name":"Oatmeal Stout","shortName":"Oatmeal Stout","description":"Oatmeal stouts include oatmeal in their grist, resulting in a pleasant, full flavor and a smooth profile that is rich without being grainy. A roasted malt character which is caramel-like and chocolate-like should be evident - smooth and not bitter. Coffee-like roasted barley and roasted malt aromas (chocolate and nut-like) are prominent. Color is dark brown to black. Bitterness is moderate, not high. Hop flavor and aroma are optional but should not overpower the overall balance if present. This is a medium- to full- bodied beer, with minimal fruity esters. Diacetyl should be absent or at extremely low levels. Original gravity range and alcohol levels are indicative of English tradition of oatmeal stout.","ibuMin":"20","ibuMax":"40","abvMin":"3.8","abvMax":"6","srmMin":"20","srmMax":"20","ogMin":"1.038","fgMin":"1.008","fgMax":"1.02","createDate":"2012-03-21 20:06:45","updateDate":"2015-04-07 15:22:53"},"breweries":[{"id":"m2lpu3","name":"Timeless Pints Brewing Company","description":"Lakewood's first microbrewery! \r\n\r\nOn Father's Day, several years ago, my son and I purchased a home brewing kit for my husband. As an Engineer and a lover of craft beer, he was excited to experiment with his own concoctions. Since his first trial run, he's produced multiple variety of stouts, ales, lagers and IPA's as well as very happy friends, family and neighbors. His love for the unique keeps him constantly in search of \"new and different\" ingredients and the hope of a perfect combination.\r\n\r\nOne hot July evening, some friends disclosed they were embarking on a new restaurant idea. They asked Chris (my husband) if he would brew the beer specifically for their new endeavor. The ABC frowns on beer sold without the proper licensing and selling from the kitchen counter is not a viable option. Thus a new venture began.\r\n\r\nWhat was once a dream is now a reality and we can now bring our own craft beer to our local Lakewood\/Long Beach community. You'll find us just behind the Long Beach Airport.","website":"http:\/\/www.timelesspints.com\/","established":"2013","isOrganic":"N","images":{"icon":"https:\/\/s3.amazonaws.com\/brewerydbapi\/brewery\/m2lpu3\/upload_v1fZ28-icon.png","medium":"https:\/\/s3.amazonaws.com\/brewerydbapi\/brewery\/m2lpu3\/upload_v1fZ28-medium.png","large":"https:\/\/s3.amazonaws.com\/brewerydbapi\/brewery\/m2lpu3\/upload_v1fZ28-large.png"},"status":"verified","statusDisplay":"Verified","createDate":"2013-08-03 22:49:34","updateDate":"2013-08-04 13:19:27","locations":[{"id":"3wVSu9","name":"Main Brewery","streetAddress":"3671 Industry Avenue","extendedAddress":"C1","locality":"Lakewood","region":"California","postalCode":"90712","phone":"(562) 490-0099","website":"http:\/\/www.timelesspints.com\/","hoursOfOperation":"Thu: 4:00 pm - 8:00 pm\r\nFri: 2:00 pm - 8:00 pm\r\nSat: 12:00 pm - 7:00 pm\r\nSun: 12:00 pm - 5:00 pm","latitude":33.8237257,"longitude":-118.1655833,"isPrimary":"Y","inPlanning":"N","isClosed":"N","openToPublic":"Y","locationType":"nano","locationTypeDisplay":"Nano Brewery","countryIsoCode":"US","yearOpened":"2013","status":"verified","statusDisplay":"Verified","createDate":"2013-08-04 13:19:09","updateDate":"2014-07-23 19:11:34","country":{"isoCode":"US","name":"UNITED STATES","displayName":"United States","isoThree":"USA","numberCode":840,"createDate":"2012-01-03 02:41:33"}}]}],"type":"beer"}],"status":"success"}

但如果搜索结果没有返回任何内容，我会得到如下结果：

{"currentPage":1,"status":"success"}

所以我需要告诉你是否返回了上面的结果。我的JSON在名为data的变量中返回到javascript中

为了确定数据中的JSON是否不包含任何结果，我尝试以下javascript代码：

if (data.data.length === undefined || data.data.length === null ) {
    $('#modal1').closeModal();
    Materialize.toast('Rate More Beers to See Statistics', 9000) // 4000 is the duration of the toast
}

我刚才也试过：

if (data.data === undefined || data.data === null ) {
    $('#modal1').closeModal();
    Materialize.toast('Rate More Beers to See Statistics', 9000) // 4000 is the duration of the toast
}

---

您应该执行以下操作来检查

数据

是否

未定义

要检查变量是否

未定义

，应使用

typeof

要检查变量是否为

null

，只需执行

！大多数情况下为变量

。但在使用此语法时，请注意，如果变量等于

0

，则它将被解释为

false

if (typeof data.data === 'undefined' || data.data === null ) {
    $('#modal1').closeModal();
    Materialize.toast('Rate More Beers to See Statistics', 9000)
}

typeof

返回变量类型的字符串表示形式。因此，在上面的示例中，它的

是“未定义的”

。所以我们只是做字符串比较

在您的尝试中：注意：这是不正确的

var data = {"currentPage":1,"status":"success"}; 
// notice that data.data = 'undefined'

// so when you do the following
if (data.data.length === 'undefined')  
// will resolve to 'undefined'.data.length
// 'undefined' does not have data and will resolve to error

---

如果

数据

始终位于返回的JSON的第一级（即与

当前页面

处于相同的级别/深度），则只需检查：

// Assuming variable `j` contains the returned JSON
if ('data' in j) {
  // Some data has been returned
}

---

您可以简单地测试

数据。数据
是否存在：

if (data.data) {
    // Code that uses data.data
} else {
    $("#modal1").closeModal();
    Materialize.toast('Rate More Beers to See Statistics', 9000);
}

你试过“data.data==undefined | | data.data.length==0”吗？你不能也这样做吗！（data.totalResults>0）
？只需使用'not'运算符：
如果（！'data'在j中）
需要
！（“数据”在j中）
。太棒了，谢谢！我做错了什么，做的类型是什么？最后一行应该是
未定义的.length
，而不是
未定义的.data.length
，因为第一行
data
没有定义。我知道。我只是在向迈克解释他在评论中要求解释的方法中做错了什么。