Question

很抱歉这个真正的新手问题，刚刚开始学习AJAX。

我想了解以下内容究竟是什么导致divMessage内容在＆＃34; myName＆＃34;文字改变了。

1）似乎Javascript函数进程经常＆＃34; listen＆＃34;，这是正常的Javscript行为，还是有任何触发器调用＆＃34; process＆＃34;反复？ 2）我们分配给＆＃34; body onload＆＃34;是否正确？将被重复执行？这种重复执行的频率是多少？ 3）如果我们想要一次执行函数过程怎么办？

4）我很困惑，因为我认为身体只会加载一次。但这是因为＆＃34; body onload＆＃34;功能＆＃34;过程＆＃34;被调用，功能过程反过来修改＆＃34; body＆＃34;通过改变divMessage，基本上让它通过＆＃34; body onload＆＃34;再次，那么＆＃34;过程＆＃34;再等等..？

非常感谢您的帮助！

<head>
  <script type="text/javascript" src="quickstart.js"></script>
</head>
<body onload='process()'>
  Server wants to know your name:
  <input type="text" id="myName" />
  <div id="divMessage" />
</body>

这里是quickstart.js处理部分

function process()
{
  // proceed only if the xmlHttp object isn't busy
  if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
  {
    // retrieve the name typed by the user on the form
    name = encodeURIComponent(
    document.getElementById("myName").value);
    // execute the quickstart.php page from the server
    xmlHttp.open("GET", "quickstart.php?name=" + name, true);
    // define the method to handle server responses
    xmlHttp.onreadystatechange = handleServerResponse;
    // make the server request
    xmlHttp.send(null);
  }
}

  // callback function executed when a message is received from the server
  function handleServerResponse()
  {
    // move forward only if the transaction has completed
    if (xmlHttp.readyState == 4)
    {
      // status of 200 indicates the transaction completed successfully
      if (xmlHttp.status == 200)
      {
        xmlResponse = xmlHttp.responseXML;
        xmlDocumentElement = xmlResponse.documentElement;
        helloMessage = xmlDocumentElement.firstChild.data;

        // display the data received from the server
        document.getElementById("divMessage").innerHTML =
                  '<i>' + helloMessage+ '</i>';
      }
    }
  }

和quickstart.php

<?php
header('Content-Type: text/xml');
echo '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>';
echo '<response>';
$name = $_GET['name'];

// generate output depending on the user name received from client
$userNames = array('YODA', 'AUDRA', 'BOGDAN', 'CRISTIAN');
if (in_array(strtoupper($name), $userNames))
  echo 'Hello, master ' . htmlentities($name) . '!';
else if (trim($name) == '')
  echo 'Stranger, please tell me your name!';
else
  echo htmlentities($name) . ', I don't know you!';

echo '</response>';
?>

Answer 1

通过关闭并尝试再次运行来找到答案。事实证明，我注释了其他代码但缓存了每1秒从handleServerResponse（）调用“进程”：

// display the data received from the server
    document.getElementById("divMessage").innerHTML =
              '<i>' + helloMessage+ '</i>';
    setTimeout('process()', 1000);

很抱歉。课程是在测试每个代码更改之前清除浏览器缓存:) 所以我想检查是否从任何其他地方调用此函数的建议是正确的。无论如何，我读了很多东西，并在尝试计算时学到了很多东西这个。非常感谢@pst！

为什么body onload = javascript函数连续执行？

1 个答案: