Sorting a list alphabetically with a modulus

Question

I don\'t have any trouble grabbing a list of elements and sorting them alphabetically, but I\'m having difficulty understanding how to do it with a modulus.

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Answer 1

1. Alphabetize your list. This is already done, in your case, but if not:

   function alphabetizeElements(a, b)
   {
       var aText = $(a).text();
       var bText = $(b).text();
       return aText > bText ? 1 : aText < bText ? -1 : 0;
   }
   var alphabetizedList = $("#myList li").sort(alphabetizeElements);
   

2. Store the alphabetized index of each element:

   $.each(alphabetizedList, function(i)
   {
       $(this).data("alphaIndex", i);
   });
   

3. Sort the alphabetized list by modulus first, then index:

   function listColumnSortFn(columns)
   {
       return function(a, b)
       {
           var aIndex = $(a).data("alphaIndex");
           var bIndex = $(b).data("alphaIndex");
           return ((aIndex % columns) - (bIndex % columns)) || (aIndex - bIndex);
       }
   }
   var columnSortedList = alphabetizedList.sort(listColumnSortFn(4));
   

4. Replace the list elements with your sorted elements:

   $("#myList li").remove();
   $("#myList").append(columnSortedList);
   

Here is the whole thing, all together:

function sortList(columns)
{
    var alphabetizedList = $("#myList li").sort(alphabetizeElements);
    $.each(alphabetizedList, function(i)
    {
        $(this).data("alphaIndex", i);
    });
    var columnSortedList = alphabetizedList.sort(listColumnSortFn(columns));
    $("#myList li").remove();
    $("#myList").append(columnSortedList);
}
function alphabetizeElements(a, b)
{
    var aText = $(a).text();
    var bText = $(b).text();
    return aText > bText ? 1 : aText < bText ? -1 : 0;
}
function listColumnSortFn(columns)
{
    return function(a, b)
    {
        var aIndex = $(a).data("alphaIndex");
        var bIndex = $(b).data("alphaIndex");
        return ((aIndex % columns) - (bIndex % columns)) || (aIndex - bIndex);
    }
}
$(function()
{
    sortList(4);
});