只在浏览器关闭时执行查询

Question

有个小问题。当浏览器或选项卡关闭时，我希望执行查询，但是如果该页面中存在任何按钮或链接，并且单击其中任何一个按钮或链接，则查询也会执行。。在这方面需要帮助

First.php

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1
/jquery.min.js"></script>

<script type="text/javascript">

 $(document).bind('keypress', function(e) {
    if (e.keyCode == 116){
      validNavigation = true;
    }
  });

  // Attach the event click for all links in the page
  $("a").bind("click", function() {
    validNavigation = true;
  });

  // Attach the event submit for all forms in the page
  $("form").bind("submit", function() {
    validNavigation = true;
  });

  // Attach the event click for all inputs in the page
  $("input[type=submit]").bind("click", function() {
    validNavigation = true;
  }); 

 window.addEventListener("beforeunload", function (e) {
 if (!validNavigation) { 
 $.ajax({
url: 'logout.php',
type: 'POST',
async: false,
timeout: 4000
});
}
})
</script>

logout.php

    <?php
$username = "root";
$password = "";
$hostname = "localhost"; 

$dbhandle = mysql_connect($hostname, $username, $password) 
 or die("Unable to connect to MySQL");
echo "Connected to MySQL<br>";


$selected = mysql_select_db("examples",$dbhandle) 
  or die("Could not select examples");

$result =  mysql_query("DELETE FROM cars WHERE id='1'");
mysql_close($dbhandle);
?>

Answer 1

浏览器卸载当前文档时触发事件“先卸载”。如果在同一页上使用窗体，则需要在按下提交时取消设置事件。

例如：window.onbeforeunload=null;

您可以在onsubmit处理程序中这样做：

<form onsubmit="cancelUnloadAndSubmit()">
  Enter name: <input type="text">
  <input type="submit">
</form>

Answer 2

将单击处理程序包装如下：

<script type="text/javascript">
  var validNavigation = false;
  $(document).ready(function() {

    $("a").click(function() {
        validNavigation = true;
    });

  });

window.addEventListener("beforeunload", function (e) {
  if (!validNavigation) { 
    // do something...
  }
})
</script>