How to create a Calculator and date/time picker on a website?

Question

WordPress

Where to read how to create just such a function: Calculation of additional services, selection of the date of the event and free time? I want to do this for the landig page (on Adobe Muse) and for WordPress. Link examples: vk.cc/4sPsQZ and http://www.dari-deed.rf/Proposal/3/Description . I'm attaching more screenshots.

Answer 1

Well, on the first site - there are hidden inputs with prices and attributes with prices in checkboxes. JS is all collected on clicks.