很多登录功能上都有个“记住密码”的功能，其实无非就是对cookie的读取。

下面展示这个功能的代码，测试方法：直接输入账号密码，提交后，刷新页面，再输入同样的账号，就可以显示

下面是login.jsp

<input type="text" id="username" class="input t1" placeholder="用户名或手机号">
<input type="password" id="password" class="input t2" placeholder="密码">
<div class="checkbox"><label><input id="jz" type="checkbox">记住密码</label></div>
<div class="login_btn"><input type="button" onclick="login()" class="btn" value="登 录"></div>

下面是login.js 

/*
*初始化调用
*/
$(function(){
	GetLastUser();
});

/*
*登录
*/
function login(){
	/*业务代码省略*/
    SetPwdAndChk();
}

/*
*从cookie中获取用户名及密码
*/
function GetLastUser() {
    var id = "49BAC005-7D5B-4231-8CEA-16939BEACD67";//GUID标识符
    var usr = GetCookie(id);
    if (usr != null) {
      document.getElementById('username').value = usr;
    } else {
      document.getElementById('password').value = "001";
    }
    GetPwdAndChk();
  }

/*
*点击登录时触发客户端事件
*/
function SetPwdAndChk() {
    //取用户名
    var usr = $.trim($('#username').val());
    //alert(usr);
    //将最后一个用户信息写入到Cookie
    SetLastUser(usr);
    //如果记住密码选项被选中
    if (document.getElementById('jz').checked == true) {
        //取密码值
        var pwd = $.trim($('#password').val());
        //alert(pwd);
        var expdate = new Date();
        expdate.setTime(expdate.getTime() + 14 * (24 * 60 * 60 * 1000));
        //将用户名和密码写入到Cookie
        SetCookie(usr, pwd, expdate);
    } else {
        //如果没有选中记住密码,则立即过期
        ResetCookie();
    }
}

function SetLastUser(usr) {
    var id = "49BAC005-7D5B-4231-8CEA-16939BEACD67";
    var expdate = new Date();
    //当前时间加上两周的时间
    expdate.setTime(expdate.getTime() + 14 * (24 * 60 * 60 * 1000));
    SetCookie(id, usr, expdate);
}

//用户名失去焦点时调用该方法
function GetPwdAndChk() {
    var usr = $.trim($('#username').val());
    var pwd = GetCookie(usr);
    if (pwd != null) {
        document.getElementById('jz').checked = true;
        document.getElementById('password').value = pwd;
    } else {
        document.getElementById('jz').checked = false;
        document.getElementById('password').value = "";
    }
}

//取Cookie的值
function GetCookie(name) {
    var arg = name + "=";
    var alen = arg.length;
    var clen = document.cookie.length;
    var i = 0;
    while (i < clen) {
        var j = i + alen;
        if (document.cookie.substring(i, j) == arg) return getCookieVal(j);
        i = document.cookie.indexOf(" ", i) + 1;
        if (i == 0) break;
    }
    return null;
}

function getCookieVal(offset) {
    var endstr = document.cookie.indexOf(";", offset);
    if (endstr == -1) endstr = document.cookie.length;
    return unescape(document.cookie.substring(offset, endstr));
}

//写入到Cookie
function SetCookie(name, value, expires) {
    var argv = SetCookie.arguments;
    //本例中length = 3
    var argc = SetCookie.arguments.length;
    var expires = (argc > 2) ? argv[2] : null;
    var path = (argc > 3) ? argv[3] : null;
    var domain = (argc > 4) ? argv[4] : null;
    var secure = (argc > 5) ? argv[5] : false;
    document.cookie = name + "=" + escape(value) + ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) + ((path == null) ? "" : ("; path=" + path)) + ((domain == null) ? "" : ("; domain=" + domain)) + ((secure == true) ? "; secure" : "");
}

function ResetCookie() {
    var usr = $.trim($('#username').val());
    var expdate = new Date();
    SetCookie(usr, null, expdate);
}