Ajax重新发送XMLHttpRequest [英] Ajax resending XMLHttpRequest

问题描述

我有一个这样的客户端js/ajax脚本:

I've got a client side js/ajax script like this:

<p>server  time  is:  <strong  id="stime">Please  wait...</strong></p>

<script>
function  updateAjax()  {
    xmlhttp  =  new  XMLHttpRequest();
    xmlhttp.onreadystatechange  =  function()  {
        if (xmlhttp.readyState==3  &&  xmlhttp.status==200)  {
            document.getElementById("stime").innerHTML=
            xmlhttp.responseText;
        }
        if  (xmlhttp.readyState==4)  {  
            xmlhttp.open("GET","date-sleep.php",true);
            xmlhttp.send();
        }
    }
    xmlhttp.open("GET","date-sleep.php",true);  
    xmlhttp.send();
}
window.setTimeout("updateAjax();",100);
</script>

在服务器端还有一个:

<?php
    echo  6;
    for  ($i=0;  $i<10;  $i++)  {
        echo  $i;
        ob_flush();  flush();
        sleep(1);
    }
?>

在第一次打开"并发送"之后，它可以正常工作，但是当服务器完成脚本并且 xmlhttp.readyState == 4 时，xmlhttp重新发送请求，但是什么也没有发生.>

After first 'open' and 'send' it works ok, but when the server finishes the script and xmlhttp.readyState == 4 then the xmlhttp resends the request but nothing happens.

推荐答案

而不是一直重复使用同一XHR对象，请尝试使用一个新对象重复该功能.至少应该可以解决您列出的不兼容问题.

Instead of re-using the same XHR object all the time, try repeating the function with a new object. This should at least fix incompatibility issues as you listed.

如果要无限循环，请尝试在其回调内重新调用Ajax函数.

Try re-calling your Ajax function inside the callback of it, if you want to loop it infinitely.

if  (xmlhttp.readyState==4) {  
     updateAjax(); //or setTimeout("updateAjax();",100); if you want a delay
}

我还建议您将 .innerHTML 方法放入

I'd also suggest putting your .innerHTML method inside the .readyState==4, which is when the requested document has completely loaded, and .status==200 which means success. Like this:

if (xmlhttp.readyState==4  &&  xmlhttp.status==200) {
       document.getElementById("stime").innerHTML=
       xmlhttp.responseText;
       updateAjax(); //or setTimeout("updateAjax();",100);
}

此外，如果您希望跨浏览器使用Ajax，则应测试浏览器是否支持 XHR您正在使用的对象:

Also, if you want your Ajax to be cross-browser, you should test if the browser supports the XHR object which you're using:

var xmlhttp = (window.XMLHttpRequest) ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");

我刚刚键入了上面的代码，但是它可以很好地添加与IE和其他浏览器的较早版本的兼容性.

I just typed the code above but it should work just fine to add compatibility with older versions of IE and other browsers.

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