localStorage 和sessionStorage 存值，取值，删除指定数据和清空的方法

var a=[{id:1,city:"bj"},{id:2,city:"sh"},{id:3,city:"wh"},{id:4,city:"cq"}
]
var val=$(obj).attr("id");
//存值 
localStorage.setItem("userInfo",JSON.stringify(a)); //存储之前数组转换为字符串
sessionStorage.setItem("select_id",val);
sessionStorage.setItem("select_id","");//值为空
//取值
var user = JSON.parse(localStorage.getItem("userInfo"));
var user1 = sessionStorage.getItem("select_id");
//删除指定数据
localStorage.removeItem("userInfo");
sessionStorage.removeItem("select_id");
//全部清空
localStorage.clear();
sessionStorage.clear();