ajax - Javascript. JSON -

i have sample json file:

{   "array": [     1,     2,     3   ],   "boolean": true,   "null": null,   "number": 123,   "object": {     "a": "b",     "c": "d",     "e": "f"   },   "string": "hello world" } 

i need object array. work want show alert there no "4" in object

tried that:

if(check == null){     alert("not exist") } 

but not working. tried put undefined instead of null not working well. should put there ?

rest working fine. know how data json. issue check function.

                    $.getjson(host_address ,function(data){                         var check = data.array[4]                         if(check == null){                             alert("not exist")                             }                     }); 

you can (i assume have usable json object you've fetched):

var data = {   "array": [     1,     2,     3   ],   "boolean": true,   "null": null,   "number": 123,   "object": {     "a": "b",     "c": "d",     "e": "f"   },   "string": "hello world" };  // grab array var stuff = data.array;  // check see if value in array if(!(4 in stuff)){  alert("not in.");    }