How to define custom sort function in javascript?

It could be that the plugin is case-sensitive. Try inputting Te instead of te. You can probably have your results setup to not be case-sensitive. This question might help.

For a custom sort function on an Array, you can use any JavaScript function and pass it as parameter to an Array's sort() method like this:

var array = ['White 023', 'White', 'White flower', 'Teatr'];

array.sort(function(x, y) {
  if (x < y) {
    return -1;
  }
  if (x > y) {
    return 1;
  }
  return 0;
});

// Teatr White White 023 White flower
document.write(array);

More Info here on Array.sort.

For Objects try this:

function sortBy(field) {
  return function(a, b) {
    if (a[field] > b[field]) {
      return -1;
    } else if (a[field] < b[field]) {
      return 1;
    }
    return 0;
  };
}