Function submitNewItem

app/src/static/js/app.js:76–90

    const [submitting, setSubmitting] = React.useState(false);

    const submitNewItem = e => {
        e.preventDefault();
        setSubmitting(true);
        fetch('/items', {
            method: 'POST',
            body: JSON.stringify({ name: newItem }),
            headers: { 'Content-Type': 'application/json' },
        })
            .then(r => r.json())
            .then(item => {
                onNewItem(item);
                setSubmitting(false);
                setNewItem('');
            });
    };

    return (
        <Form onSubmit={submitNewItem}>