How to check if a json key exists?

Question

So, I get some JSON values from the server but I don\'t know if there will be a particular field or not.

So like:

{ \"regatta_name\":\"ProbaRegatta\"         


        

Answer 1

just before read key check it like before read

JSONObject json_obj=new JSONObject(yourjsonstr);
if(!json_obj.isNull("club"))
{
  //it's contain value to be read operation
}
else
{
  //it's not contain key club or isnull so do this operation here
}

isNull function definition

Returns true if this object has no mapping for name or
if it has a mapping whose value is NULL. 

official documentation below link for isNull function

http://developer.android.com/reference/org/json/JSONObject.html#isNull(java.lang.String)

Answer 2

I used hasOwnProperty('club')

var myobj = { "regatta_name":"ProbaRegatta",
    "country":"Congo",
    "status":"invited"
 };

 if ( myobj.hasOwnProperty("club"))
     // do something with club (will be false with above data)
     var data = myobj.club;
 if ( myobj.hasOwnProperty("status"))
     // do something with the status field. (will be true with above ..)
     var data = myobj.status;

works in all current browsers.

Answer 3

You can check this way where 'HAS' - Returns true if this object has a mapping for name. The mapping may be NULL.

if (json.has("status")) {
   String status = json.getString("status"));
}

if (json.has("club")) {
   String club = json.getString("club"));
}

You can also check using 'isNull' - Returns true if this object has no mapping for name or if it has a mapping whose value is NULL.

if (!json.isNull("club"))
    String club = json.getString("club"));

Answer 4

You can use the JsonNode#hasNonNull(String fieldName), it mix the has method and the verification if it is a null value or not

Answer 5

Try this:

let json=yourJson

if(json.hasOwnProperty(yourKey)){
    value=json[yourKey]
}

Answer 6

Try this

if(!jsonObj.isNull("club")){
    jsonObj.getString("club");
}