Как прочитать массив JSON с JavaScript, чтобы получить значение, если он существует ⇐ JAVA

[Anonymous]

Вот мой код JSON. Я храню этот json в массиве. < /P>

Код: Выделить всё

{
"kind": "urlshortener#url",
"id": "http://example.com/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": "https://www.hike.com/?utm_source=facebook-pp&utm_medium=anvy&utm_campaign=naveen-2&utm_term=%2F&utm_content=100",
"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"
}
}
}

}
In the above JSON, how can we get the existence of analytics -> day -> countries?
I want to know whether the countries exists in day or not first, if it's not, show some value. Если он есть, он попытается извлечь счет частичной страны. < /P>
Я пробую это с последних 5 часов без удачи.

Код: Выделить всё

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;

}

The above code is working fine if there is countries in day, but sometimes, in my JSON there will be no platforms part, in that case it's giving me

Код: Выделить всё

Uncaught TypeError: Cannot read property 'map' of undefined
< /code>
Мне нужен способ проверить, существуют ли платформы, если это будет подсчитать, если это не дает какого -то другого значения переменной. Но когда у него нет ключа, он показывает ошибку «неопределенного счета». < /P>
var month_inclicks = arr.analytics.month.countries.filter(function(el) { return el.id == "IN"; })[0].count;

Как мы можем установить значение по умолчанию, если ключ, который мы ищем, не существует?

Подробнее здесь: https://stackoverflow.com/questions/327 ... -it-exists