Simple answer is, client-side code cannot interact with Server-side code. However, once the server-side controls such as Buttons have been downloaded and converted to HTML, you can then interact with them using their HTML attributes.
You can learn how can JavaScript stylize the HTML content here,
https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement.style[
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But remember, you cannot manipulate the server-side code or controls. Only the HTML rendered output of their can be manipulated inside the browser using JavaScript (and/or its libraries such as jQuery).