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20-dynamic-forms.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>20-dynamic-forms</title>
</head>
<body>
<div id="root"></div>
<!-- URL's changed for react libs. `React.useState not defined in [email protected]` -->
<script src="https://unpkg.com/[email protected]/umd/react.development.js"></script>
<script src="https://unpkg.com/[email protected]/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/@babel/[email protected]/babel.js"></script>
<script type="text/babel">
const UserNameForm = () => {
const [userName, setuserName] = React.useState("");
const isLowerCase = userName === userName.toLowerCase();
const errorMsg = isLowerCase ? null : `Username must be lowercase`;
const handleSubmit = (e) => {
e.preventDefault();
alert(`You entered: ${userName}`);
};
const handleChange = (e) => setuserName(e.target.value);
return (
<form onSubmit={handleSubmit}>
<p>
<label htmlFor="userNameInput">Username: </label>
<input id="userNameInput" type="text" onChange={handleChange} />
<span
style={{ display: "block", color: "red", marginTop: "0.5rem" }}
>
{errorMsg}
</span>
</p>
<button disabled={errorMsg} type="submit">
Submit
</button>
</form>
);
};
ReactDOM.render(<UserNameForm />, document.getElementById("root"));
</script>
</body>
</html>