How do I store variables within the browser cache? (JS)

You can use WebStorage of an object, such as a localStorage of the fields:

Imagine that you have two input fields one with ID = name and another ID = lastname you can do localstorage of these fields in this way:

var lastname = document.getElementById("lastname").value;
var name = document.getElementById("name").value;
localStorage.setItem("lastname", lastname);
localStorage.setItem("name", name);

where the first part within the parentheses represents the name of the "attribute" of localStorage, and can be referenced by localStorage.lastname / localStorage.name

In addition to localStorage , there is also sessionStorage ( link , which turns out to be safer, since it is session-based, and complemented with an authentication system, can be time-controlled