window.addEventListener('beforeunload', (event) => {

    localStorage.setItem("new_qus_id", $('.responseId').attr('id'));

    var new_qus_no = localStorage.getItem('new_qus_id');
    console.log(new_qus_no);

});

if (localStorage.getItem('new_qus_id') != '') {
    var question_id = localStorage.getItem('new_qus_id');
} else {
    var question_id = "<?php echo $question_id ; ?>";
}

我不认为这里提出的解决方案是100%正确的，因为窗口。onbeforeunload事件不仅在浏览器/选项卡关闭时被调用(这是必需的)，而且在所有其他几个事件上也被调用。(可能不需要)

有关可以触发window.onbeforeunload的事件列表的更多信息，请参阅此链接

http://msdn.microsoft.com/en-us/library/ms536907 (VS.85) . aspx

There is a very specific use case in which any suggestion to use sessionStorage instead of localStorage does not really help. The use-case would be something as simple as having something stored while you have at least one tab opened, but invalidate it if you close the last tab remaining. If you need your values to be saved cross-tab and window, sessionStorage does not help you unless you complicate your life with listeners, like I have tried. In the meantime localStorage would be perfect for this, but it does the job 'too well', since your data will be waiting there even after a restart of the browser. I ended up using a custom code and logic that takes advantage of both.

I'd rather explain then give code. First store what you need to in localStorage, then also in localStorage create a counter that will contain the number of tabs that you have opened. This will be increased every time the page loads and decreased every time the page unloads. You can have your pick here of the events to use, I'd suggest 'load' and 'unload'. At the time you unload, you need to do the cleanup tasks that you'd like to when the counter reaches 0, meaning you're closing the last tab. Here comes the tricky part: I haven't found a reliable and generic way to tell the difference between a page reload or navigation inside the page and the closing of the tab. So If the data you store is not something that you can rebuild on load after checking that this is your first tab, then you cannot remove it at every refresh. Instead you need to store a flag in sessionStorage at every load before increasing the tab counter. Before storing this value, you can make a check to see if it already has a value and if it doesn't, this means you're loading into this session for the first time, meaning that you can do the cleanup at load if this value is not set and the counter is 0.

8.5年过去了，最初的问题一直没有得到答案。

当浏览器关闭时，没有一个标签。

这个基本代码片段将为您提供两全其美的服务。仅在浏览器会话期间存在的存储(如sessionStorage)，但也可以在选项卡之间共享(localStorage)。

它完全通过localStorage来实现这一点。

function cleanup(){
    // place whatever cleanup logic you want here, for example:
    // window.localStorage.removeItem('my-item')
}

function tabOpened(){
    const tabs = JSON.parse(window.localStorage.getItem('tabs'))
    if (tabs === null) {
        window.localStorage.setItem('tabs', 1)
    } else {
        window.localStorage.setItem('tabs', ++tabs)
    }
}

function tabClosed(){
    const tabs = JSON.parse(window.localStorage.getItem('tabs'))
    if (tabs === 1) {
        // last tab closed, perform cleanup.
        window.localStorage.removeItem('tabs')
        cleanup()
    } else {
        window.localStorage.setItem('tabs', --tabs)
    }
}

window.onload = function () {
    tabOpened();
}

window.onbeforeunload = function () {
    tabClosed();
}

    if(localStorage.getItem("visit") === null) {
      localStorage.setItem('visit', window.location.hostname);
      console.log(localStorage.getItem('visit'));
    } 
      else if(localStorage.getItem('visit') == 'localhost'){
            console.log(localStorage.getItem('visit'));
      }
    else {
     console.log(localStorage.getItem('visit'));
    }
   $(document).ready(function(){
      $("#clickme").click(function(){
         localStorage.setItem('visit', '0');
      });
   });  
   window.localStorage.removeItem('visit');

localStorage.removeItem(key);  //item

localStorage.clear(); //all items