sessionStorage关闭单个窗口，数据就会消失，localStorag可以长期保存数据，有特定的storage事件。
https://blog.csdn.net/ruangong1203/article/details/52841135
1.html <!DOCTYPE html> <html> <head lang="en"> <title>A</title> </head> <body> //第一步：第一次打开1.html的时候，什么都没存储 //第三部：我再打开1.html,我发现多了数据foo=bar,为什么我们能发现那，storage检测到了 <script> window.addEventListener("storage", function (e) { alert(e.newValue); }); </script> </body> </html> 2.html <!DOCTYPE html> <html> <head lang="en"> <title>B</title> </head> <body> //第二步：我打开了2.html,把数据foo=bar存储了 <script> localStorage.clear(); localStorage.setItem('foo', 'bar'); </script> </body> </html> 3.html 自己监测自己（了解） <!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"/> <title>A</title> </head> <body> <button id="btn">存储数据</button> <script> var orignalSetItem = localStorage.setItem; localStorage.setItem = function(key,newValue){ var setItemEvent = new Event("setItemEvent"); setItemEvent.newValue = newValue; window.dispatchEvent(setItemEvent); orignalSetItem.apply(this,arguments); } window.addEventListener("setItemEvent", function (e) { alert(e.newValue); }); var btn=document.getElementById("btn"); btn.onclick=function(){ localStorage.setItem("nm","abc"); } </script> </body> </html>