javascript 等待 AJAX 请求完成？
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Waiting for AJAX request to finish?
提问by Riess Howder
I have a problem that is confusing me at the moment. I am using ajax to get some ID's from a website. Once it's complete I want to store the ID's in a variable for further processing. I have my code laid out like this:
我有一个问题，目前让我感到困惑。我正在使用 ajax 从网站获取一些 ID。完成后，我想将 ID 存储在变量中以供进一步处理。我的代码如下所示：
var ids;
function get_ids() { ... Get the ID's from the site and store them in the global variable ids ... }
get_ids();
alert(ids.length);
As you can see ids will always be 0 because the script will continue to run before the ajax request in get_ids has had a chance to respond.
如您所见，ids 将始终为 0，因为脚本将在 get_ids 中的 ajax 请求有机会响应之前继续运行。
What's the best way to what I'm trying to do? I want to wait until get_ids has finished.
我正在尝试做的最好的方法是什么？我想等到 get_ids 完成。
回答by SLaks
You need to make get_idstake a callback parameter and call it when it receives a response.
您需要get_ids获取一个回调参数并在收到响应时调用它。
For example:
例如：
function get_ids(callback) {
...
response: function(data) {
...
callback(data);
}
...
}
get_ids(function(ids) {
...
});
回答by David Fullerton
It depends on your AJAX framework, but pretty much any framework will allow you to specify a function to run when the AJAX request is complete. In JQuery:
这取决于您的 AJAX 框架，但几乎任何框架都允许您指定在 AJAX 请求完成时运行的函数。在 JQuery 中：
function get_ids_complete() {
alert(ids.length);
}
function get_ids() {
$.get('/ids', function (data) {
// do something with the data
get_ids_complete();
});
}
回答by Munzilla
If you're using plain old javasript, you can call a function to run after the AJAX has completed like so:
如果您使用的是普通的旧 javasript，您可以调用一个函数在 AJAX 完成后运行，如下所示：
ajaxCall.onreadystatechange=function()
{
if (ajaxCall.readyState==4 && ajaxCall.status==200)
{
//do your ID stuff here
}
}
回答by user1032402
I'm using synchronous AJAX in situations like that; it's a blocking call, which I ordinarily avoid, but I don't see an alternative.
我在这种情况下使用同步 AJAX；这是一个阻塞调用，我通常会避免，但我没有看到替代方法。
See Synchronous AJAX
请参阅同步 AJAX
