Add native support for classMap and styleMap

[MohamedElmdary]

Describe the problem

Idea

Currently, svelte is evolving and getting way better, simpler, powerful, and solid. but sadly most svelte-ui frameworks implement its own version of styleMap & classMap.

Also we should provide a default style and class attribute in custom element (can be used optionally) which gonna make developing framework much easier

What is classMap & styleMap?

<!-- Current -->
<div  class={`c1 ${someVariable ? 'c2' : '' }`} ></div>

<!-- Map -->
<div class={['c1', { 'c2': someVariable } ]} ></div>

Describe the proposed solution

I would love to see this feature stable in svelte5 as svelte5 is really very promising with runes and snippets. I will try to implement it on my own wish I can do it and will open PR

Alternatives considered

alternative, Svelte might introduce a public method/ compiler macro / runes or whatever it's name which user can use and transform it in compile time into regular template syntax if it's any better

Importance

would make my life easier

[brunnerh]

Duplicate of:

• https://github.com/sveltejs/svelte/issues/9044

[MohamedElmdary]

@brunnerh Thanks for mentioning that issue ... sadly I was having some real fun implementing it but it's ok hope to see multi class directive support in svelte 5