you can build your own data system to provide the specific use case for your client. It's like a cms for your specific use case from your client @arnez

I want something that doesn't need db to interact with. Interactions are made with file. And I want that inside my website not like separated project. Is it doable?

you can do that by creating a file inside your website folder and the client can change stuff inside the file your website reads from this file.

For example you have this todoList in your project:

export const todoLists = [
    {
        id: 1,
        title: "Todo #1",
        content: "hello world"
    },
    {
        id: 2,
        title: "Todo #2",
        content: "I am a text"
    },
    {
        id: 3,
        title: "Todo #3",
        content: "some other text"
    }
]

Send this file to the client and tell him, that he can change for example the title from Todo #2 just by changing it. After the change he can send the file back (or directly upload it somewhere or whatever)

This is a little bit clunky because they could mess up whole code if they are clunky

I don't want to give them direct access to the code

i want them to be able to change on the website at /admin for example i just don't want to use cms i want to convert excel file to this as they know excel the best

and also i don't want to pay for extra hosting costs for cms

yea, the client can destroy your whole project with it. CMS are safe.. (in most cases). You can try to integrate a excel to json converter. Enter your excel and your website get's json. The problem is: the data (file or only it's contents) need to be saved somewhere. And it costs more to save a whole file then saving the data inside it

np, please mark solution