docs: function getStep ( xPct, xSteps, snap, value ) {
  
          if ( value === 100 ) {
              return value;
          }
  
          var j = getJ( value, xPct ), a, b;
  
          // If 'snap' is set, steps are used as fixed points on the slider.
          if ( snap ) {
  
              a = xPct[j-1];
              b = xPct[j];
  
              // Find the closest position, a or b.
              if ((value - a) > ((b-a)/2)){
                  return b;
              }
  
              return a;
          }
  
          if ( !xSteps[j-1] ){
              return value;
          }
  
          return xPct[j-1] + closest(
                  value - xPct[j-1],
                  xSteps[j-1]
              );
      }