Count of all substrings

function searchSubstring()
{
    var haystack = "We are living in an yellow submarine. We don't have anything else. Inside the submarine is very tight. So we are drinking all the day. We will move out of it in 5 days.";
    var needle = document.getElementById("problem3").value;
    //case insensitive
    haystack = haystack.toLowerCase();
    needle = needle.toLowerCase();
    var count = 0;
    var index = haystack.indexOf(needle);
    if (index >= 0) {
        count++;
    }
    while ((index = haystack.indexOf(needle, index+1)) && index != -1)
    {
        count++;
    }
    cons.innerHTML = count;

}