在 windows 7 上对 xampp 进行最基本的 ajax 工作以检查互联网连接

Question

在提交表单之前调用 onclick="return check_internet_conn()" 以查看是否有互联网连接，（我将在移动设备上执行此操作，xampp 也会在移动设备上进行。我的测试发生在 windows 7)，这将请求 check_internet_connection.php 文件来检查互联网连接（最好不要检查某个服务器上是否存在图像以通过 javascript 检查互联网连接）。 check_internet_connection.php 工作正常，但我永远无法获得 javascript ajax、jQuery ajax，也无法获得 javascript fetch()、return文件内容。

<div class="container">
  <form action="processQuestion.php" method="post">
   <div class="form-group">
     <label for="question">Write your question here:</label>
     <textarea class="form-control" rows="7" id="question_txt" name="question"></textarea>
   </div>
   <button type="submit" class="btn btn-primary" onclick="return check_internet_conn()">Submit Question</button> 
  </form>
  <p id="submit_error_no_internet" class="warning"></p>
</div>

这是 PHP 文件

<?PHP

try {
@   $connected = fsockopen("www.example.com", 80);
    if ($connected) {
        fclose($connected);
        echo "Connected";
    }
}   

catch(Exception $e) {
  echo 'Message: ' .$e->getMessage();
}

finally {
  echo "Not Connected!";
}

?>

下面是 ajax 和 js fetch() 的三种不同尝试，并添加了调试功能。

<script src="jquery/jquery-3.5.1.slim.min.js"></script>
<script src="bootstrap-4.5.3-dist/js/bootstrap.bundle.min.js"></script>
<script>

function check_internet_conn() {
    $.get("http://localhost/crud/check_internet_connection.php", function(data, status){
            switch(data) {
            case "Not Connected!":
                document.getElementById("submit_error_no_internet").innerHTML = "No Internet connection, connect to internet.";
                return false;
                break;
            case "ConnectedNot Connected!":
                return true;
                break;
            default:
                document.getElementById("submit_error_no_internet").innerHTML = "Nothing works";
            } 
        });
}

function check_internet_conn() {

    async function getText(file) {
        let myObject = await fetch(file);
        let myText = await myObject.text();
        switch(myText) {
        case "Not Connected!":
            document.getElementById("submit_error_no_internet").innerHTML = "No Internet connection, connect to internet.";
            return false;
            break;
        case "ConnectedNot Connected!":
            return true;
            break;
        default:
            document.getElementById("submit_error_no_internet").innerHTML = "Nothing works";
        }
    }

  getText("http://localhost/crud/check_internet_connection.php");
  
}


function check_internet_conn() {

    var myXmlhttp = new XMLHttpRequest();
    myXmlhttp.onreadystatechange = function() {
      if (this.readyState == 4 && this.status == 200) {
        document.getElementById("submit_error_no_internet").innerHTML = this.responseText;
        switch(this.responseText) {
            case "Not Connected!":
                document.getElementById("submit_error_no_internet").innerHTML = "No Internet connection, connect to internet.";
                return false;
                break;
            case "ConnectedNot Connected!":
                return true;
                break;
            default:
                document.getElementById("submit_error_no_internet").innerHTML = "Nothing works";
        } 
      }
    };
    myXmlhttp.open("GET", "http://localhost/crud/check_internet_connection.php");
    myXmlhttp.send();
    document.getElementById("submit_error_no_internet").innerHTML = myXmlhttp.status + " " + myXmlhttp.readyState;
}

</script>

我曾尝试在 Firefox 和 Chrome 中进行调试，但没有成功。没有错误消息。

Answer 1

我会做类似的事情：

<button onclick="checkConnection()">Check connection</button>

function checkConnection() {
$(document).ready(function() {
  $.ajax({
      url: "yourUrl",
      success: function(result) {
          if(result) {
          // you are connected
          } else {
          // you are not connected
          }
      },
      error: function(error) {
          // do something sad
      }
  });
});

function is_connected() {
$connected = @fsockopen("www.example.com", 80); 
if ($connected){
    $is_conn = true; //action when connected
    fclose($connected);
}else{
    $is_conn = false; //action in connection failure
}
echo($is_conn);
die();
}

在 windows 7 上对 xampp 进行最基本的 ajax 工作以检查互联网连接

Getting the most basic ajax working on xampp on windows 7 to check for internet connectivity

html

javascript

xampp

ajax

jquery