code: function valueSet ( input, fireSetEvent ) {
  
              var values = asArray(input);
              var isInit = scope_Locations[0] === undefined;
  
              // Event fires by default
              fireSetEvent = (fireSetEvent === undefined ? true : !!fireSetEvent);
  
              values.forEach(setValue);
  
              // Animation is optional.
              // Make sure the initial values were set before using animated placement.
              if ( options.animate && !isInit ) {
                  addClassFor(scope_Target, options.cssClasses.tap, options.animationDuration);
              }
  
              // Now that all base values are set, apply constraints
              scope_HandleNumbers.forEach(function(handleNumber){
                  setHandle(handleNumber, scope_Locations[handleNumber], true, false);
              });
  
              setZindex();
  
              scope_HandleNumbers.forEach(function(handleNumber){
  
                  fireEvent('update', handleNumber);
  
                  // Fire the event only for handles that received a new value, as per #579
                  if ( values[handleNumber] !== null && fireSetEvent ) {
                      fireEvent('set', handleNumber);
                  }
              });
          }
docs: Set the slider value.