function nextInLine(arr, item) {
    //Your code here
    arr.push(item);
    return item;
    //return arr.shift(); sonucu After: [2,3,4,5,6] olur
}

var testArr = [1,2,3,4,5];

console.log("Before: " + JSON.stringify(testArr));
console.log(nextInLine(testArr, 6));
console.log("After: " + JSON.stringify(testArr));