前端开发中的应用与实践：使用Ajax函数

// HTML
<button id="loadDataBtn">加载数据</button>
<ul id="dataList"></ul>

// JavaScript
const loadDataBtn = document.getElementById('loadDataBtn');
const dataList = document.getElementById('dataList');

loadDataBtn.addEventListener('click', () => {
  const xhr = new XMLHttpRequest();
  xhr.open('GET', 'data.json', true);
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      const data = JSON.parse(xhr.responseText);
      data.forEach(item => {
        const li = document.createElement('li');
        li.textContent = item.name;
        dataList.appendChild(li);
      });
    }
  };
  xhr.send();
});

<form id="myForm">
  <input type="text" name="username" placeholder="用户名" />
  <input type="password" name="password" placeholder="密码" />
  <button type="submit">提交</button>
</form>

<script>
  const form = document.getElementById('myForm');

  form.addEventListener('submit', event => {
    event.preventDefault();

    const xhr = new XMLHttpRequest();
    xhr.open('POST', 'submit.php', true);
    xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
    xhr.onreadystatechange = function() {
      if (xhr.readyState === 4 && xhr.status === 200) {
        const response = JSON.parse(xhr.responseText);
        console.log(response);
      }
    };
    const formData = new FormData(form);
    const encodedData = new URLSearchParams(formData).toString();
    xhr.send(encodedData);
  });
</script>