when and why use the class with JavaScript, kindly help

As a frontend developer, I always use the functional programming style for my apps.

When I want to create an object, I just state a variable and fill it, such as let object = {}

I am really confused about why and when to use the class with JavaScript, if I use the class to create an object, things are going to be troublesome, I need to state a class and create an object by using it.
Kindly help why and when I should use the class and need some interprets