Javascript 带计时器的 Jquery/Ajax 调用
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Jquery/Ajax call with timer
提问by John
I have a php page that echos out rows from a database. I want to call it via jquery/ajax every 30 seconds. But I also want to be able to call the page at any time so that if I add a record via the form, once the form submits I want the page via called to ajax to update the results right away. Can anyone point me in the right direction or provide some base code so I can try to figure this out? Still very new to jquery/ajax.
我有一个 php 页面，可以从数据库中回显出行。我想每 30 秒通过 jquery/ajax 调用它。但我也希望能够随时调用页面，以便如果我通过表单添加记录，一旦表单提交，我希望页面通过调用 ajax 来立即更新结果。谁能指出我正确的方向或提供一些基本代码，以便我可以尝试解决这个问题？对 jquery/ajax 来说还是很新的。
回答by treeface
If you want to set something on a timer, you can use JavaScript's setTimeoutor setIntervalmethods:
如果你想在计时器上设置一些东西，你可以使用 JavaScript 的setTimeout或setInterval方法：
setTimeout ( expression, timeout );
setInterval ( expression, interval );
Where expressionis a function and timeoutand intervalare integers in milliseconds. setTimeoutruns the timer once and runs the expressiononce whereas setInterval will run the expressionevery time the intervalpasses.
其中expression是一个函数，timeout和interval是以毫秒为单位的整数。setTimeout运行计时器一次并运行expression一次，而 setInterval 将在expression每次interval通过时运行。
So in your case it would work something like this:
所以在你的情况下，它会像这样工作：
setInterval(function() {
//call $.ajax here
}, 5000); //5 seconds
As far as the Ajax goes, see jQuery's ajax()method. If you run an interval, there is nothing stopping you from calling the same ajax()from other places in your code.
就 Ajax 而言，请参阅 jQuery 的ajax()方法。如果您运行一个时间间隔，则没有什么可以阻止您从ajax()代码中的其他地方调用相同的内容。
If what you want is for an interval to run every 30 seconds until a user initiates a form submission...and then create a new interval after that, that is also possible:
如果您想要的是每隔 30 秒运行一次间隔，直到用户启动表单提交......然后在此之后创建一个新的间隔，这也是可能的：
setInterval()returns an integer which is the ID of the interval.
setInterval()返回一个整数，它是间隔的 ID。
var id = setInterval(function() {
//call $.ajax here
}, 30000); // 30 seconds
If you store that ID in a variable, you can then call clearInterval(id)which will stop the progression.
如果将该 ID 存储在变量中，则可以调用clearInterval(id)它来停止进程。
Then you can reinstantiate the setInterval()call after you've completed your ajax form submission.
然后，您可以setInterval()在完成 ajax 表单提交后重新实例化调用。
