test-insert.html

<!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>Test Insert</title>
</head>
<body>
  <div>
  <input type="text" id="name">
  <input type="number" id="groese" step="0.05" min="1.60" max="2.60">
  <input type="date" id="date">
  <button id="ins">add</button>
  </div>

  <div>
  <input type="text" id="iso" placeholder="Kürzel" minlength="3" maxlength="3">
  <input type="text" id="country" placeholder="Land">
  <button id="ins-land">add</button>
  </div>  
</body>
<script>
  const ins = document.getElementById('ins').addEventListener('click', async ev=>{
    const response = await fetch(`/test`, {
      method: 'POST',
      body: JSON.stringify({
        Name: document.getElementById('name').value,
        size : parseFloat(document.getElementById('groese').value),
        Date: document.getElementById('date').value
      })
    });
    if( !response.ok ) {
      const message = `Error: ${response.status}`;
    } else if( 200 <= response.status && response.status <= 299 ) {
      //success
      result = await response.json();
      message = `${response.statusText} ${result.id} `;
    } else {
      const message = `Error: ${response.statusText}`;
    }
    alert(message);
  });

  const del = document.getElementById('ins-land').addEventListener('click', async ev=>{
    const response = await fetch(`/country`, {
      method: 'POST',
      body: JSON.stringify({
        ISO: document.getElementById('ISO').value,
        Country: document.getElementById('country').value
      })
    });
    if( !response.ok ) {
      const message = `Error: ${response.status}`;
    } else if( 200 <= response.status && response.status <= 299 ) {
      //success
      result = await response.json();
      message = `${response.statusText} ${result.id} `;
    } else {
      const message = `Error: ${response.statusText}`;
    }
    alert(message);
  });


</script>
</html>