I have the following situation:

.my-nice-class {

  max-width: 90%;

  max-height: 90%;

}

This code lies in the first <style>...</style> in the html page.
I would like to override this global css, by setting for instance new properties values like in the example below:

.my-nice-class {

  max-width: 40%;

  max-height: 40%;

}

How can I accomplish this with pure Javascript?

Thank you all,

Nano