DataTables sorts strings instead of numeric

I am using jquery.datatables to show numbers in datatables columns. Numbers are formatted to have spaces in between thousands unit (like 123 456 789). Unfortunately, this number formatting provoques a string sorting instead of a number sorting (see the screenshot at the end of this question).

I have identified that:

• function _fnSort(oSettings, bApplyClasses) { is the core function for sorting.
• In this function, the dynamic function sorting approach is used (the one executed if if (!window.runtime) { is true)

• The string sorting functions used are the two following functions.

  /*
  * text sorting
  */
  "string-asc": function(a, b) {
      var x = a.toLowerCase();
      var y = b.toLowerCase();
      return ((x < y) ? -1 : ((x > y) ? 1 : 0));
  },
  
  "string-desc": function(a, b) {
      var x = a.toLowerCase();
      var y = b.toLowerCase();
      return ((x < y) ? 1 : ((x > y) ? -1 : 0));
  },
  

My knowledge in javascript is pretty poor, what would be the best approach here?

1. Tweak the string sorting function to detect the number thousands formatted case, and do the comparison (I guess this would be pretty slow on large data set).
2. Provide a numerical sorting function dedicated for number thousands formatted? In that case
   • how would you code that?
   • how could I indicate to the core sorting function, to use this special numerical sorting function?

Here is what the sorting look like by now: