XMLHttpRequest打开和发送:如何判断它是否有效 [英] XMLHttpRequest Open and Send: How to tell if it worked
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问题描述
正如标题中所述,我的问题是,是否可以判断XMLhttpRequest中的open和send方法是否真的有效?有指标吗?
示例代码:
As is in the title, my question is, Is is possible to tell if the open and send methods from XMLhttpRequest actually worked? Is there any indicator? example code:
cli = new XMLHttpRequest();
cli.open('GET', 'http://example.org/products');
cli.send();
我正在尝试对此进行故障处理编码,但我需要能够判断是否请求失败,所以我可以处理它。
I'm trying to code in fault handling to this, but I need to be able to tell if the request failed so I can handle it.
推荐答案
这是一个异步操作。您的脚本在发送请求时继续执行。
This is an an asynchronous operation. Your script continues its execution while the request is being sent.
您使用回调检测状态更改:
You detect the state changes using a callback :
var cli = new XMLHttpRequest();
cli.onreadystatechange = function() {
if (cli.readyState === 4) {
if (cli.status === 200) {
// OK
alert('response:'+cli.responseText);
// here you can use the result (cli.responseText)
} else {
// not OK
alert('failure!');
}
}
};
cli.open('GET', 'http://example.org/products');
cli.send();
// note that you can't use the result just here due to the asynchronous nature of the request
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