I am a beginner in Java script and want to know about few lines of code

var input =store ["cemboard-queryExecutor-333374"];
var test = input[0];
console.log(test);
var smsarr = [" NEISMSRecieve_Failure_Network_Perc_Cont_Sum","NEISMSRecieve_Failure_Subscriber_Perc_Cont_Sum","NEISMSSend_Failure_Network_Perc_Cont_Sum","NEISMSSend_Failure_Subscriber_Perc_Cont_Sum"];
var sum="";
for(var i = 0; i < smsarr.length-1 ; i++)
{
console.log([smsarr]);
console.log("**");
console.log(input[0]);
sum = sum + input[0][smsarr];
console.log(sum);
}

I am getting undefined value in sum . and i am not able to understand what is store and how it is defined.