javascript - How do I fix the problem with the capitalization checker?

Question

I have a one problem. This my TodoList Project: https://codepen.io/BerkayAkgurgen/pen/OJRqjPg (Please Check The Link ?f you want to better understand the problem.) I'm trying to prevent the same words from being added to the list as items. I'm trying to control it with the "toLowerCase" command inside. But it keeps adding the same words because their letter sizes are different, for example: "Berkay" "berkay" I want these two words not to be included even if their letter sizes are different.

 function addTodo(e) {
    const newTodoValue = todoInput.value.trim();
    const newTodoValuee = todoInput.value.trim().toLowerCase();
    let todos = getTodosFromStorage();
    if (newTodoValue === "") {
        console.log("merhaba");
    } else if (todos.includes(newTodoValuee)) {
        e.preventDefault();
        console.log("Ayn? Todo");
        todoInput.value = "";
        return false;
    } else {
        addTodoToUI(newTodoValue);
        addTodoToStorage(newTodoValue);
    }
    e.preventDefault();
}

Answer 1

In this case, todos.includes(newTodoValuee) requires to be extended since your case is different.

Instead use this: if(todos.some(a=>a.trim().toLowerCase() == newTodoValuee))