使用Javascript将多个输入字段合并为一个输入字段？

<form>
  <input type="text" id="firstName" placeholder="First Name">
  <input type="text" id="lastName" placeholder="Last Name">
  <input type="email" id="email" placeholder="Email">
  <button type="button" onclick="mergeFields()">Merge Fields</button>
</form>

function mergeFields() {
  var firstName = document.getElementById("firstName").value;
  var lastName = document.getElementById("lastName").value;
  var email = document.getElementById("email").value;

  var mergedField = firstName + " " + lastName + " (" + email + ")";
  
  // 将合并后的值设置到一个新的输入字段中
  document.getElementById("mergedField").value = mergedField;
}

<input type="text" id="mergedField" readonly>

<form>
  <input type="text" id="firstName" placeholder="First Name">
  <input type="text" id="lastName" placeholder="Last Name">
  <input type="email" id="email" placeholder="Email">
  <button type="button" onclick="mergeFields()">Merge Fields</button>
</form>

<input type="text" id="mergedField" readonly>

<script>
function mergeFields() {
  var firstName = document.getElementById("firstName").value;
  var lastName = document.getElementById("lastName").value;
  var email = document.getElementById("email").value;

  var mergedField = firstName + " " + lastName + " (" + email + ")";
  
  document.getElementById("mergedField").value = mergedField;
}
</script>