This filter allows you modify the info window template that is used on individual store pages.
In this example the data from a custom field called “my_textinput” is added after the address details:
The <% ... %> and <%= ... %> code is used by the Underscore
library to execute JS code, and to print the correct JSON data when the HTML template is rendered.
This filter is located in /frontend/underscore-functions.php.
The code needs to be placed in the functions.php file inside your active theme folder.