I need custom javascript in some CMS page. First, I simply created the following: '..\themes\child_classic\assets\js\custom.js'; the file is correctly loaded at the bottom of the HTML code. Then I realized a simple button "Click me!" as test: it works correctly as well, no error message in the browser console. Obviously on any other page: "Uncaught TypeError: Cannot read properties of null (reading 'addEventListener') at custom.js:4:10"... That doesn't invalidate the PrestaShop's functioning (until now) but it makes me understand I should set the whole thing better. Where am I wrong? Thanks in advance.