React Js Disable submit button if element found in array

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <script src="https://unpkg.com/react@17.0.2/umd/react.development.js"></script>
    <script src="https://unpkg.com/react-dom@17.0.2/umd/react-dom.development.js"></script>
    <script src="https://unpkg.com/@babel/standalone@7.14.7/babel.min.js"></script>
  </head>

<body>
    <div id="app"></div>
    <script type="text/babel">
      const { useState, useEffect, useRef } = React;

function App() {
        const [inputValue, setInputValue] = useState("");
        const [todos, setTodos] = useState([
          { id: 1, title: "Font Awesome Icons" },
          { id: 2, title: "React" },
          { id: 3, title: "Vue" },
          { id: 4, title: "Javascript" },
        ]);

const handleInputChange = (event) => {
          setInputValue(event.target.value);
        };

const handleSubmit = (event) => {
          event.preventDefault();

// Check if the input value already exists in the todos array (case-insensitive)
          const isDuplicate = todos.some(
            (todo) => todo.title.toLowerCase() === inputValue.toLowerCase()
          );

if (isDuplicate) {
            // Input value already exists, do not submit the form
            return;
          }

// Add the new todo to the todos array
          const newTodo = { id: todos.length + 1, title: inputValue };
          setTodos([...todos, newTodo]);

// Clear the input field
          setInputValue("");
        };

return (
          <div className="container">
            <h3>React Js Disable submit button if element found in array</h3>
            <form onSubmit={handleSubmit}>
              <input
                type="text"
                value={inputValue}
                onChange={handleInputChange}
              />
              <button
                type="submit"
                disabled={
                  !inputValue ||
                  todos.some(
                    (todo) =>
                      todo.title.toLowerCase() === inputValue.toLowerCase()
                  )
                }
              >
                Add Todo
              </button>
            </form>
            <ul>
              {todos.map((todo) => (
                <li key={todo.id}>{todo.title}</li>
              ))}
            </ul>
          </div>
        );
      }
      ReactDOM.render(<App />, document.getElementById("app"));
    </script>

form {
        display: flex;
        margin-bottom: 20px;
      }

input[type="text"] {
        flex: 1;
        padding: 10px;
        font-size: 16px;
        border: 1px solid #ccc;
        border-radius: 4px;
        outline: none;
      }

button[type="submit"] {
        padding: 10px 20px;
        font-size: 16px;
        background-color: #007bff;
        color: #fff;
        border: none;
        border-radius: 4px;
        cursor: pointer;
      }

button[type="submit"]:disabled {
        background-color: #ccc;
        cursor: not-allowed;
      }

ul {
        list-style-type: none;
        padding: 0;
      }

li {
        padding: 10px 0;
        border-bottom: 1px solid #ccc;
        font-size: 16px;
      }
    </style>
  </body>
</html>

 
<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <script src="https://unpkg.com/react@17.0.2/umd/react.development.js"></script>
    <script src="https://unpkg.com/react-dom@17.0.2/umd/react-dom.development.js"></script>
    <script src="https://unpkg.com/@babel/standalone@7.14.7/babel.min.js"></script>
  </head>
​
  <body>
    <div id="app"></div>
    <script type="text/babel">
      const { useState, useEffect, useRef } = React;
​
      function App() {
        const [inputValue, setInputValue] = useState("");
        const [todos, setTodos] = useState([
          { id: 1, title: "Font Awesome Icons" },
          { id: 2, title: "React" },
          { id: 3, title: "Vue" },
          { id: 4, title: "Javascript" },
        ]);
​
        const handleInputChange = (event) => {
          setInputValue(event.target.value);
        };
​
        const handleSubmit = (event) => {
          event.preventDefault();
​
          // Check if the input value already exists in the todos array (case-insensitive)
          const isDuplicate = todos.some(
            (todo) => todo.title.toLowerCase() === inputValue.toLowerCase()
          );
​
          if (isDuplicate) {
            // Input value already exists, do not submit the form
            return;
          }
​
          // Add the new todo to the todos array
          const newTodo = { id: todos.length + 1, title: inputValue };
          setTodos([...todos, newTodo]);
​
          // Clear the input field
          setInputValue("");
        };
​
        return (
          <div className="container">
            <h3>React Js Disable submit button if element found in array</h3>
            <form onSubmit={handleSubmit}>
              <input
                type="text"
                value={inputValue}
                onChange={handleInputChange}
              />
              <button
                type="submit"
                disabled={
                  !inputValue ||
                  todos.some(
                    (todo) =>
                      todo.title.toLowerCase() === inputValue.toLowerCase()
                  )
                }
              >
                Add Todo
              </button>
            </form>
            <ul>
              {todos.map((todo) => (
                <li key={todo.id}>{todo.title}</li>
              ))}
            </ul>
          </div>
        );
      }
      ReactDOM.render(<App />, document.getElementById("app"));
    </script>
​
    <style>
      .container {
        max-width: 500px;
        margin: 0 auto;
        padding: 20px;
        border-radius: 8px;
        box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
      }
​
      form {
        display: flex;
        margin-bottom: 20px;
      }
​
      input[type="text"] {
        flex: 1;
        padding: 10px;
        font-size: 16px;
        border: 1px solid #ccc;
        border-radius: 4px;
        outline: none;
      }
​
      button[type="submit"] {
        padding: 10px 20px;
        font-size: 16px;
        background-color: #007bff;
        color: #fff;
        border: none;
        border-radius: 4px;
        cursor: pointer;
      }
​
      button[type="submit"]:disabled {
        background-color: #ccc;
        cursor: not-allowed;
      }
​
      ul {
        list-style-type: none;
        padding: 0;
      }
​
      li {
        padding: 10px 0;
        border-bottom: 1px solid #ccc;
        font-size: 16px;
      }
    </style>
  </body>
</html>
​