如何处理XHR错误显示消息? [英] How to handle XHR error display messages?

问题描述

我正尝试使用XHR从另一个来源获取一些内容，如下所示:

I'm trying to fetch some content from another source using XHR as shown below:

function fetchPage(str)
{
    if(str=="")
    {
        document.getElementById("table").innerHTML="";
        resetFilters();
        $('#progress').hide();  //fetching progress bar <div>
        return;
    }
    if (window.XMLHttpRequest) // code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp=new XMLHttpRequest();
    else // code for IE6, IE5
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");

    xmlhttp.onreadystatechange=postCallback;
    xmlhttp.open("GET", "fetch.php?url=http://www.sis.itu.edu.tr/tr/ders_programlari/LSprogramlar/prg.php?fb="+str, true);
    xmlhttp.send();

// any stuff that goes here will happen before callback
//  (this is a good place to update a UI element showing a call is resolving.)
//  (for example a spinner or text saying "fetching")
$('#progress').show();
progressFetching();
switch(xmlhttp.readyState){ //loading bar adjustments
    case 0:
        $('.bar').css("width","0%");
        $('.bar').text("0%");
        break;
    case 1:
        $('.bar').css("width","25%");
        $('.bar').text("25%");
        break;
    case 2:
        $('.bar').css("width","50%");
        $('.bar').text("50%");
        break;
    case 3:
        $('.bar').css("width","75%");
        $('.bar').text("75%");
        break;
}
}



function postCallback()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200){
    progressDone();   //loading is finished
    $('#error').hide();
    document.getElementById("table").innerHTML=xmlhttp.responseText;                     

    // continue to process post callback.
    resetFilters();
}
else {
    // report error with fetch

    /*if(xmlhttp.status==404 || xmlhttp.responseText == "")
        $('#error').show();*/
    //$('#error').show();
}
}

我希望我的页面在发生连接超时或计算机没有互联网连接(可能在闲逛时发生断开连接)或网页无法获取对方内容的任何其他情况下显示错误来源.

I want my page to display error when connection timeout occurs, or when the computer doesn't have an internet connection (maybe a disconnection occurred while hanging around) or any other situation where the webpage fails to fetch the contents of the other source.

使用上面的代码，在else块中，如果我在/* */注释部分中使用if(xmlhttp.status==404 || xmlhttp.responseText == "")，则不会收到错误，除非它不是404错误.如果我进入//注释部分，则在开始获取过程直至完成之前，即在xmlhttp.readyState = 0至xmlhttp.readyState = 4之间，将显示错误.如何使用这些属性或其他属性显示连接错误消息?

Using the code above, in the else block, if I go for if(xmlhttp.status==404 || xmlhttp.responseText == "") in the /* */ comment section, I won't get an error unless its not a 404 error. If i go for // comment section, error will be displayed after the fetching process is started until it is completed, i.e. between xmlhttp.readyState = 0 through xmlhttp.readyState = 4. How can I display connection error messages using these attributes or something else?

感谢您的关注:)

推荐答案

问题是我在先前问题中的模板存在缺陷.我相信这样做会更好，因为它创建了一个闭包来传递您需要使用的变量.

The problem is my template in prior question was flawed. I believe this will work better because it creates a closure to pass the variable you need to work with.

再一次，我没有对此进行测试，因此它可能存在输入错误和错误-除了调用postCallback()的方式并向其添加参数之外，我也没有进行任何更改.

Once again, I did not test this so it might have typos and bugs -- nor did I change anything except how postCallback() is invoked and added a parameter to it.

function fetchPage(str)
{
    if(str=="")
    {
        document.getElementById("table").innerHTML="";
        resetFilters();
        $('#progress').hide();  //fetching progress bar <div>
        return;
    }
    var xmlhttp;

    if (window.XMLHttpRequest) // code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp=new XMLHttpRequest();
    else // code for IE6, IE5
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");

    xmlhttp.onreadystatechange=function () { postCallback(xmlhttp); };
    xmlhttp.open("GET", "fetch.php?url=http://www.sis.itu.edu.tr/tr/ders_programlari/LSprogramlar/prg.php?fb="+str, true);
    xmlhttp.send();

// any stuff that goes here will happen before callback
//  (this is a good place to update a UI element showing a call is resolving.)
//  (for example a spinner or text saying "fetching")
$('#progress').show();
progressFetching();
switch(xmlhttp.readyState){ //loading bar adjustments
    case 0:
        $('.bar').css("width","0%");
        $('.bar').text("0%");
        break;
    case 1:
        $('.bar').css("width","25%");
        $('.bar').text("25%");
        break;
    case 2:
        $('.bar').css("width","50%");
        $('.bar').text("50%");
        break;
    case 3:
        $('.bar').css("width","75%");
        $('.bar').text("75%");
        break;
}
}



function postCallback(xmlhttp)
{
if (xmlhttp.readyState==4 && xmlhttp.status==200){
    progressDone();   //loading is finished
    $('#error').hide();
    document.getElementById("table").innerHTML=xmlhttp.responseText;                     

    // continue to process post callback.
    resetFilters();
}
else {
    // report error with fetch

    /*if(xmlhttp.status==404 || xmlhttp.responseText == "")
        $('#error').show();*/
    //$('#error').show();
}
}

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