How to change the style of a specific list item on click in React.js?

I am a beginner when it comes to coding with React or JS.

I was trying to create a To-Do list wherein I can add or delete tasks (which I have already accomplished). However, I wanted to add another functionality of a ‘Done’ button which will strike through the specific task item on click.

My react code areas of interest look like this:

function Todo(){

    const [tasks, settask] = useState([]);
    const [newtask, setnewtask] = useState("");

    function handle_change(event){
        setnewtask(event.target.value);
    }

    function update_todo(){

        if(newtask!=""){        
            settask(t => [...t, newtask]);
            setnewtask("");}
    }

    function delete_task(index){
        const a = tasks.filter((_, i) => i!=index);
        settask(a);
    }

    function strike(index){
        // const striked = {textDecoration: "line-through"};
        tasks[index].style.textDecoration = "line-through";  
    }


    return(
        <div id="main">
            <h1>To-Do List</h1>
            <div id="add">
                <input type="text" id="add_item" placeholder='Enter your task' value={newtask} onChange={handle_change}></input>
                <input type="button" id="add_button" onClick={update_todo} value="Submit"></input>
            </div>
            <div id="list">
                <ol>{tasks.map((element,index) => <li key={index}>
                    <div className="list_item">{element}</div>
                    <div className="button_container">
                        <button className="delete" onClick={() => delete_task(index)}>Delete</button>
                        <button className="done" onClick={() => {strike(index)}}>Done</button>
                        </div>
                    </li>)}
                </ol>
            </div>
        </div>
    )
}

I have implemented the above code, but the done button functionality is doing nothing, I tried multiple ways but none of them is working.

enter image description here