blocks|key|850990|text|响应的状态xhr.status+(通常)用于确定请求是否成功。xhr.readyState只是用来判断请求的状态，比如“尚未发送”(0)、“完成并收到响应”(4)等。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|850991|服务器负责提供status，而用户代理提供readyState。|850992|entityMap^0|5|A|V|E|0|7|6|L|A|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|I|$]]

The status of the response, <code>xhr.status</code>, is (generally) used to determine whether the request was successful or not. <code>xhr.readyState</code> is simply used to determine the state of the request, such as "has not yet been sent" (0), "complete and response received" (4), etc. 

The server is responsible for providing the <code>status</code>, while the user agent provides the <code>readyState</code>.

blocks|key|850966|text|状态指示服务器响应是否正常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|850967|总而言之，当你得到一个状态时|850968|850969|+500+-+599:服务器出现错误|blockquote|offset|length|style|BOLD|850970|850971|400+-+499:这是一个客户端错误(例如:找不到404页)|850972|300+-+399:随后存在重定向|850973|200+-+299:，那么它是正确的|850974|100+-+199:表示信息消息|850975|850976|然后status==200会给你一条消息，服务器会说：‘嘿，伙计，我来做工作！’|850977|entityMap^0|0|0|0|1|A|0|0|0|A|0|0|A|0|0|A|0|0|A|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|10|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|12|8|@$H|13|I|14|J|K]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|15|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|16|8|@$H|17|I|18|J|K]]|9|@]|A|$]]|$1|O|3|P|5|6|7|19|8|@$H|1A|I|1B|J|K]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1C|8|@$H|1D|I|1E|J|K]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1F|8|@$H|1G|I|1H|J|K]]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|1J|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|Y|$]]

status indicates if server response is ok. 
In general words, when you got an status
<blockquote>
500 - 599: the server had an error
400 - 499: this is a client error (Ex: 404 page not found)
300 - 399: then exists a redirect
200 - 299: then it is correct and
100 - 199: means information message
</blockquote>
Then the status==200 is getting you a message where the server says: 'Hey man I do the work!'

blocks|key|851016|text|我的类比是:一辆载着病人的急救车要去hospital.In，这种情况下，家庭(客户端)和医院(服务器)需要跟踪两件事|type|unstyled|depth|inlineStyleRanges|entityRanges|data|851017|在此process.(status)期间，|offset|length|style|CODE|851018|急救队到达了患者的医院successfully.(readyState)|unordered-list-item|851019|Health更新|851020|851021|如果是readyState+===+4和status+===+200，意味着一切都是right.In，就像ajax调用一样。|851022|entityMap^0|0|B|6|0|P|A|0|0|0|3|G|K|E|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@$D|T|E|U|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|V|8|@$D|W|E|X|F|G]]|9|@]|A|$]]|$1|K|3|L|5|J|7|Y|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|10|8|@$D|11|E|12|F|G]|$D|13|E|14|F|G]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|Q|$]]

my analogy : An ambulance carrying a patient is going to a hospital.In this scenario family(client) and hospital (server) needs to keep track of two things

<ul>
<li>Ambulance reached hospital successfully.(<code>readyState</code>)</li>
<li>Health updates of patient during this process.(<code>status</code>)</li>
</ul>

If <code>readyState === 4</code> and <code>status === 200</code>, means everything is all right.In the same way ajax call works.

blocks|key|4465314|text|readyState保存XMLHttpRequest的状态。从0更改为4：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4465315|4465316|+0:请求未初始化|blockquote|4465317|4465318|1:服务器连接已建立|4465319|2:收到请求|4465320|3:处理请求|4465321|4:请求完成，响应就绪状态200："OK“404:找不到页面|4465322|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|R|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|S|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|P|$]]

readyState Holds the status of the XMLHttpRequest. Changes from 0 to 4:

<blockquote>
 0: request not initialized
 
 1: server connection established
 
 2: request received
 
 3: processing request
 
 4: request finished and response is ready
 status 200: "OK"
 404: Page not found
</blockquote>

blocks|key|854265|text|假设您的服务器端代码有一个错误。您请求该页面，当服务器完成流传输响应时，readyState将为4，但状态码将为500+(或500左右)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|854266|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Consider you have an error on your server side code. You request the page, and the readyState will be 4 when the server finishes streaming the response, but the status code will be 500 (or 500-something).

blocks|key|854424|text|readyState+保存XMLHttpRequest的状态。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|854425|0:请求未初始化|854426|1:服务器连接已建立|854427|2:收到请求|854428|3:处理请求|854429|4:请求完成，响应就绪|854430|status+返回请求的状态号|854431|200："OK“|854432|403：“禁止”|854433|404：“未找到”|854434|有关响应消息的详细信息，请访问|854435|https://www.w3schools.com/tags/ref_httpmessages.asp|854436|entityMap|0|LINK|mutability|MUTABLE|url^0|0|A|B|K|0|0|0|0|0|0|0|6|7|4|0|0|0|0|0|0|1F|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1D|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|1E|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|1F|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|1G|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|1H|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|R|3|S|5|6|7|1N|8|@]|D|@]|E|$]]|$1|T|3|U|5|6|7|1O|8|@]|D|@]|E|$]]|$1|V|3|W|5|6|7|1P|8|@]|D|@]|E|$]]|$1|X|3|Y|5|6|7|1Q|8|@]|D|@]|E|$]]|$1|Z|3|10|5|6|7|1R|8|@]|D|@$9|1S|A|1T|1|1U]]|E|$]]|$1|11|3|-4|5|6|7|1V|8|@]|D|@]|E|$]]]|12|$13|$5|14|15|16|E|$17|10]]]]

readyState Holds the status of the XMLHttpRequest.

0: request not initialized 

1: server connection established

2: request received 

3: processing request 

4: request finished and response is ready

status Returns the status-number of a request

200: "OK"

403: "Forbidden"

404: "Not Found"

for details of response messages
visit

<a href="https://www.w3schools.com/tags/ref_httpmessages.asp" rel="nofollow noreferrer">https://www.w3schools.com/tags/ref_httpmessages.asp</a>

blocks|key|850955|text|readyState指的是请求的响应-当您完成对响应的检索并且有需要查看的内容时，它是4。实际值仍然未知，因此您需要检查已返回的status。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|850956|entityMap^0|0|A|1S|6|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

The <code>readyState</code> refers to the response of the request - it is 4 when you have finished retrieving the response and there is something to look at. The actual value is still not known, so you need to check the <code>status</code> that has been returned.

blocks|key|851067|text|只有当我们从服务器获得响应时，才会执行onreadystatechange=function()。如果我们从服务器得到响应，意味着我们的请求完成了，用4表示。200告诉我们它的状态是正确的。"4:请求已完成，响应就绪状态200“如果找不到页面，我们将得到状态404。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|851068|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

onreadystatechange=function() executes only when we get the response from the server.
If we get response from the server means our request is finished which is indicated by 4.And 200 tells us its status that is correct.
"4: request finished and response is ready status 200"
We get status 404 if the page is not found.

blocks|key|854456|text|示例:您(客户端)向您的女友(服务器)发送一个包，但需要她的签名(200签名或404签名)。您可以检查包裹的状态(0+-在邮局，4-+out用于投递)。一旦包裹离开设施，它将被标记为递送(4)。但是，如果你的女朋友在包裹到达时不在家，它将作为未签名的邮件返回邮局(404)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|854457|因此，可以接收关于包裹的状态(4)和递送是否成功的状态(404)。使用AJAX，可以向服务器发出请求。一旦获得了所请求的信息(这包括服务器的状态-是否找到数据/文档)，则在显示任何内容之前，将其发送回接收器(客户端)进行分析。|854458|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Illustration:
You (client) send a package to your girlfriend (server), but requires her signature (200 - signed or 404 - not signed). You can check the status of your package (0 - at post office, 4 - out for delivery). Once the package leaves the facility, it will be marked out for delivery (4). But if your girlfriend is not at home when the package arrives, it will return to the post office as not signed (404).

So, it is possible for a status to be received regarding the package (4) and a status of whether delivery was successful (404). With AJAX, a request can be made to a server. Once the requested information has been obtained (this includes the status of the server - whether the data/document was found), then it is sent back to the receiver (client) for analysis, prior to displaying any content.

<pre><code>xmlhttp.onreadystatechange = function()
{
 if (xmlhttp.readyState == 4 &amp;&amp; xmlhttp.status == 200)
 {
 document.getElementById("myDiv").innerHTML = xmlhttp.responseText;
 }
}
</code></pre>

Above code is from:<a href="http://www.w3schools.com/ajax/ajax_xmlhttprequest_onreadystatechange.asp" rel="noreferrer">http://www.w3schools.com/ajax/ajax_xmlhttprequest_onreadystatechange.asp</a>.

Question:

According to this tutorial:

<pre><code>readyState: 4: request finished and response is ready 

status: 200: "OK" 

When readyState is 4 and status is 200, the response is ready:
</code></pre>

since when <code>xmlhttp.readyState == 4</code>, response is ready, why do we still need <code>xmlhttp.status == 200</code>? what is the difference between <code>xmlhttp.readyState == 4</code> and <code>xmlhttp.status == 200</code>?

readyState vs status==200

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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xmlhttp.onreadystatechange = function(){    if (xmlhttp.readyState == 4 && xmlhttp.status == 200)    {        document.getElementById("myDiv").innerHTML = xmlhttp.responseText;    }}上面的代码来自：。问题：根据本教程：

问readyState vs status==200
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回答 9

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