How can i solve that problem

Tell us what’s happening:

Your code so far

function nextInLine(testArr, item) {
  // Your code here
  var item1=nextInline([2],1);
  return item1;  // Change this line
}
var test= nextInline([2],1);
// Test Setup
var testArr = [1,2,3,4,5];
testArr.push(6);
testArr.shift();

// Display Code
console.log("Before: " + JSON.stringify(testArr));
console.log(nextInLine(testArr, 6)); // Modify this line to test
console.log("After: " + JSON.stringify(testArr));

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 6.1; rv:29.0) Gecko/20100101 Firefox/29.0.

Link to the challenge:
https://www.freecodecamp.org/challenges/stand-in-line