function parseNumStr(numStr) {
    if (/^\s*-?Infinity\s*$/.test(numStr)) { // check for positive or negative Infinity and return that
      return parseFloat(numStr);
    }
    return parseFloat(numStr.replace(/[^0-9.eE-]/g, ''));
  }
@ngdoc method
@methodOf ui.grid.class:rowSorter
@name sortNumber
@description Sorts numerical values.  Handles nulls and undefined through calling handleNulls
@param {object} a sort value a
@param {object} b sort value b
@returns {number} normal sort function, returns -ve, 0, +ve