To check replication status, mongodb has rs.status() inbuilt function.

abc:PRIMARY> rs.status
function () { return db._adminCommand("replSetGetStatus"); }

rs.status ouput

If secondary is synced and wasn’t created with slaveDelayoption then optime and optimeDate of secondary should be equal or close (if there are current operations) to those of primary. In that case stateStr should be equal to SECONDARY. So if secondary is synced you should see output similar to this (one member has been removed from output for clarity):

abc:PRIMARY> rs.status()
{
        "set" : "abc",
        "date" : ISODate("2016-06-22T03:23:58.327Z"),
        "myState" : 1,
        "members" : [
                {
                        "_id" : 0,
                        "name" : "PC114:27001",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 72635,
                        "optime" : Timestamp(1466563991, 607),
                        "optimeDate" : ISODate("2016-06-22T02:53:11Z"),
                        "electionTime" : Timestamp(1466495099, 1),
                        "electionDate" : ISODate("2016-06-21T07:44:59Z"),
                        "configVersion" : 1,
                        "self" : true
                },
                {
                        "_id" : 1,
                        "name" : "PC114:27002",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 70742,
                        "optime" : Timestamp(1466563991, 607),
                        "optimeDate" : ISODate("2016-06-22T02:53:11Z"),
                        "lastHeartbeat" : ISODate("2016-06-22T03:23:57.854Z"),
                        "lastHeartbeatRecv" : ISODate("2016-06-22T03:23:57.855Z"),
                        "pingMs" : 0,
                        "syncingTo" : "PC114:27001",
                        "configVersion" : 1
                },
                {
                        "_id" : 2,
                        "name" : "PC114:27003",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 70742,
                        "optime" : Timestamp(1466563991, 607),
                        "optimeDate" : ISODate("2016-06-22T02:53:11Z"),
                        "lastHeartbeat" : ISODate("2016-06-22T03:23:57.854Z"),
                        "lastHeartbeatRecv" : ISODate("2016-06-22T03:23:57.855Z"),
                        "pingMs" : 0,
                        "syncingTo" : "PC114:27001",
                        "configVersion" : 1
                }
        ],
        "ok" : 1
}