这是我的 JSON 代码。我将此 json 存储在一个数组中。
{
"kind": "urlshortener#url",
"id": "http://goo.gl/2FIrtF",
"longUrl": "http://hike.com/?utm_source=facebook",
"status": "OK",
"created": "2015-09-22T13:45:53.645+00:00",
"analytics": {
"allTime": {
"shortUrlClicks": "1",
"longUrlClicks": "1",
"referrers": [
{
"count": "1",
"id": "unknown"
}
],
"countries": [
{
"count": "1",
"id": "IN"
}
],
"browsers": [
{
"count": "1",
"id": "Chrome"
}
],
"platforms": [
{
"count": "1",
"id": "Macintosh"
}
]
},
"month": {
"shortUrlClicks": "1",
"longUrlClicks": "1",
"referrers": [
{
"count": "1",
"id": "unknown"
}
],
"countries": [
{
"count": "1",
"id": "IN"
}
],
"browsers": [
{
"count": "1",
"id": "Chrome"
}
],
"platforms": [
{
"count": "1",
"id": "Macintosh"
}
]
},
"week": {
"shortUrlClicks": "1",
"longUrlClicks": "1",
"referrers": [
{
"count": "1",
"id": "unknown"
}
],
"countries": [
{
"count": "1",
"id": "IN"
}
],
"browsers": [
{
"count": "1",
"id": "Chrome"
}
],
"platforms": [
{
"count": "1",
"id": "Macintosh"
}
]
},
"day": {
"shortUrlClicks": "0",
"longUrlClicks": "0"
},
"twoHours": {
"shortUrlClicks": "0",
"longUrlClicks": "0"
}
},
"result": {
"kind": "urlshortener#url",
"id": "http://goo.gl/2FIuvF",
"longUrl": "http://hike.com/?utm_source=facebook",
"status": "OK",
"created": "2015-09-22T13:45:53.645+00:00",
"analytics": {
"allTime": {
"shortUrlClicks": "1",
"longUrlClicks": "1",
"referrers": [
{
"count": "1",
"id": "unknown"
}
],
"countries": [
{
"count": "1",
"id": "IN"
}
],
"browsers": [
{
"count": "1",
"id": "Chrome"
}
],
"platforms": [
{
"count": "1",
"id": "Macintosh"
}
]
},
"month": {
"shortUrlClicks": "1",
"longUrlClicks": "1",
"referrers": [
{
"count": "1",
"id": "unknown"
}
],
"countries": [
{
"count": "1",
"id": "IN"
}
],
"browsers": [
{
"count": "1",
"id": "Chrome"
}
],
"platforms": [
{
"count": "1",
"id": "Macintosh"
}
]
},
"week": {
"shortUrlClicks": "1",
"longUrlClicks": "1",
"referrers": [
{
"count": "1",
"id": "unknown"
}
],
"countries": [
{
"count": "1",
"id": "IN"
}
],
"browsers": [
{
"count": "1",
"id": "Chrome"
}
],
"platforms": [
{
"count": "1",
"id": "Macintosh"
}
]
},
"day": {
"shortUrlClicks": "0",
"longUrlClicks": "0"
},
"twoHours": {
"shortUrlClicks": "0",
"longUrlClicks": "0"
}
}
}
}
在上面的 JSON 中，我们如何获取分析 -> 天 -> 国家/地区的存在？
我想先知道这些国家是否存在于白天，如果不存在，则显示一些值。如果存在，它将尝试获取特定国家/地区的计数。
我在过去 5 个小时里一直在尝试这个，但没有任何运气。
if(arr.analytics.day.countries !== undefined) {
function thingscount(arr, platf) {
var x = arr.analytics.day.countries.map(function(el) {
return (platf.indexOf(el.id) != -1) ? parseInt(el.count) : 0; });
var count = 0;
for (var i = 0; i < x.length; i++) count += x[i];
return count;
}
var one = thingscount(arr, ["US"]);
}else{
var one = 0;
}
如果白天有国家/地区，上面的代码工作正常，但有时，在我的 JSON 中不会有平台部分，在这种情况下它会给我
Uncaught TypeError: Cannot read property 'map' of undefined
我需要一种方法来检查平台是否存在，是否进行计数，是否没有为变量提供其他值。
更新:
我使用下面的代码来获取 IN 的计数。
当它有 IN 键和值时，它就会给我结果。但是当它没有 IN 键时，它会显示“未定义计数”错误。
var Month_inclicks = arr.analytics.month.countries.filter(function(el) { return el.id == "IN"; })[0].count;
如果我们要查找的键不存在，如何设置默认值？
最佳答案
虽然这不是 JSON，但我假设它是一个 javascript 对象。话虽这么说，您需要考虑利用 hasOwnProperty 方法或 in 关键字。
示例:
if (arr.total.limited.hasOwnProperty('platforms')) { //do stuff
或
if ('platforms' in arr.total.limited) { //do something
关于javascript - 如何使用 Javascript 读取 JSON 数组以获取值(如果存在)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32783754/