Add an EventListener in a html class

I have a calendar that as button to change the month view this buttons have a class name of 'pika-prev' and 'pika-next' im trying to the this: 

Did you try this steps:

  1. First you should create parameters in the javascript block for the WidgetIdentifiers.
  2. Then you need to create input parameters in the client action for all the javascript parameters.
  3. Assign the input parameters to the parameters of the javascript.
  4. When calling the client action, fill the input parameters with the Widget Identifiers.

Cheers

But since the button to change the month doenst have an widgetid only the html class name

I understand you... I share with you three ways that can solve your issue: