cookie和本地存储的区别

// 使用js创建cookie
document.cookie="username=John Doe";
// 添加一个过期时间
document.cookie="username=John Doe; expires=Thu, 18 Dec 2013 12:00:00 GMT";
// 使用path 告诉浏览器cookie的路径
document.cookie="username=John Doe; expires=Thu, 18 Dec 2013 12:00:00 GMT; path=/";


//读取
var x = document.cookie;
// 修改  旧的值将会被覆盖
document.cookie="username=John Smith; expires=Thu, 18 Dec 2013 12:00:00 GMT; path=/";

// 删除 删除 cookie 非常简单。您只需要设置 expires 参数为以前的时间即可
document.cookie = "username=; expires=Thu, 01 Jan 1970 00:00:00 GMT";

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

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