HTMLFormElement: elements

<form id="my-form">
  <label>
    :
    <input type="text" name="username" />
  </label>
  <label>
    :
    <input type="text" name="full-name" />
  </label>
  <label>
    :
    <input type="password" name="password" />
  </label>
</form>

const inputs = document.getElementById("my-form").elements;
const inputByIndex = inputs[0];
const inputByName = inputs["username"];

const inputs = document.getElementById("my-form").elements;

// Iterate over the form controls
for (let i = 0; i < inputs.length; i++) {
  if (inputs[i].nodeName === "INPUT" && inputs[i].type === "text") {
    // Update text input
    inputs[i].value.toLocaleUpperCase();
  }
}

const inputs = document.getElementById("my-form").elements;

// Iterate over the form controls
for (let i = 0; i < inputs.length; i++) {
  // Disable all form controls
  inputs[i].setAttribute("disabled", "");
}