JS中使用Cookie实现记住密码以及设置密码过期时间

// 设置cookie
function setCookie(cname, cvalue, exdays) {
  var d = new Date();
  d.setTime(d.getTime() + (exdays * 24 * 60 * 60 * 1000));
  var expires = "expires=" + d.toUTCString();
  document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}

// 获取cookie
function getCookie(cname) {
  var name = cname + "=";
  var decodedCookie = decodeURIComponent(document.cookie);
  var ca = decodedCookie.split(';');
  for(var i = 0; i <ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) === ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) === 0) {
      return c.substring(name.length, c.length);
    }
  }
  return "";
}

// 检查是否存在记住密码的cookie
function checkRememberMe() {
  var username = getCookie("username");
  var password = getCookie("password");

  if (username !== "" && password !== "") {
    // 填充用户名和密码
    document.getElementById("username").value = username;
    document.getElementById("password").value = password;
  }
}

// 登录按钮点击事件
function login() {
  var username = document.getElementById("username").value;
  var password = document.getElementById("password").value;
  var rememberMe = document.getElementById("rememberMe").checked;

  // 处理登录逻辑...

  if (rememberMe) {
    // 设置记住密码的cookie
    setCookie("username", username, 7);
    setCookie("password", password, 7);
  } else {
    // 清除记住密码的cookie
    setCookie("username", "", -1);
    setCookie("password", "", -1);
  }
}

// 在页面加载时检查是否存在记住密码的cookie
window.onload = function() {
  checkRememberMe();
};
``` 

```html
<input type="text" id="username" placeholder="Username">
<input type="password" id="password" placeholder="Password">
<label><input type="checkbox" id="rememberMe"> Remember me</label>
<button οnclick="login()">Login</button>