a snippet that allows for having different sorters for each column

SlickGrid simple sorter.js

// Define some sorting functions
function NumericSorter(a, b) {
  var x = a[sortcol], y = b[sortcol];
  return sortdir * (x == y ? 0 : (x > y ? 1 : -1));
}
function RatingSorter(a, b) {
  var xrow = a[sortcol], yrow = b[sortcol];
  var x = xrow[3], y = yrow[3];
  return sortdir * (x == y ? 0 : (x > y ? 1 : -1));
}

// Configure the columns
var columns = [
  {id:"published", name:"Published", field:"published", sortable: true, sorter:NumericSorter, formatter:DateCellFormatter},
  {id:"title", name:"Title", field:"title", sortable: true, sorter:NumericSorter, formatter:TitleCellFormatter},
  {id:"publisher", name:"Publisher", field:"publisher", sorter:NumericSorter, sortable: true},
  {id:"rating", name:"Rating", field:"rating", sortable: true, sorter:RatingSorter, formatter:RatingCellFormatter},
];

$(function() {
  var grid = new Slick.Grid(".datatable", data_view.getItems(), columns, options);
  grid.onSort.subscribe(function(e, args) {
    sortdir = args.sortAsc ? 1 : -1;
    sortcol = args.sortCol.field;

    data_view.sort(args.sortCol.sorter, sortdir);
    args.grid.invalidateAllRows();
    args.grid.render();
  });
});