jQuery，简单的轮询示例
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jQuery, simple polling example
提问by Mike
I'm learning jQuery, and I'm trying to find a simple code example that will poll an API for a condition. (ie, request a webpage every few seconds and process the results)
我正在学习 jQuery，并且我正在尝试找到一个简单的代码示例，该示例将轮询 API 以获取条件。（即，每隔几秒请求一个网页并处理结果）
I'm familiar with how to do AJAX in jQuery, I just can't seem to find the "proper" way of getting it to execute on a "timer".
我熟悉如何在 jQuery 中执行 AJAX，但我似乎无法找到让它在“计时器”上执行的“正确”方式。
回答by Johnny Craig
function doPoll(){
$.post('ajax/test.html', function(data) {
alert(data); // process results here
setTimeout(doPoll,5000);
});
}
回答by chrisjleu
Here's a helpful article on long polling(long-held HTTP request) using jQuery. A code snippet derived from this article:
这是一篇关于使用 jQuery进行长轮询（长期保持的 HTTP 请求）的有用文章。源自本文的代码片段：
(function poll() {
setTimeout(function() {
$.ajax({
url: "/server/api/function",
type: "GET",
success: function(data) {
console.log("polling");
},
dataType: "json",
complete: poll,
timeout: 2000
})
}, 5000);
})();
This will make the next request only after the ajax request has completed.
这只会在 ajax 请求完成后发出下一个请求。
A variation on the above that will execute immediately the first time it is called before honouring the wait/timeout interval.
在遵守等待/超时间隔之前，将在第一次调用时立即执行上述变体。
(function poll() {
$.ajax({
url: "/server/api/function",
type: "GET",
success: function(data) {
console.log("polling");
},
dataType: "json",
complete: setTimeout(function() {poll()}, 5000),
timeout: 2000
})
})();
回答by Boopathi Rajaa
From ES6,
从 ES6 开始，
var co = require('co');
var $ = require('jQuery');
// because jquery doesn't support Promises/A+ spec
function ajax(opts) {
return new Promise(function(resolve, reject) {
$.extend(opts, {
success: resolve,
error: reject
});
$.ajax(opts);
}
}
var poll = function() {
co(function *() {
return yield ajax({
url: '/my-api',
type: 'json',
method: 'post'
});
}).then(function(response) {
console.log(response);
}).catch(function(err) {
console.log(err);
});
};
setInterval(poll, 5000);
- Doesn't use recursion (function stack is not affected).
- Doesn't suffer where setTimeout-recursion needs to be tail-call optimized.
- 不使用递归（函数堆栈不受影响）。
- 在 setTimeout-recursion 需要尾调用优化的地方不会受到影响。
回答by genesis
function poll(){
$("ajax.php", function(data){
//do stuff
});
}
setInterval(function(){ poll(); }, 5000);
回答by PeeHaa
function make_call()
{
// do the request
setTimeout(function(){
make_call();
}, 5000);
}
$(document).ready(function() {
make_call();
});
回答by nobar
jQuery.Deferred()can simplify management of asynchronous sequencing and error handling.
jQuery.Deferred()可以简化异步排序和错误处理的管理。
polling_active = true // set false to interrupt polling
function initiate_polling()
{
$.Deferred().resolve() // optional boilerplate providing the initial 'then()'
.then( () => $.Deferred( d=>setTimeout(()=>d.resolve(),5000) ) ) // sleep
.then( () => $.get('/my-api') ) // initiate AJAX
.then( response =>
{
if ( JSON.parse(response).my_result == my_target ) polling_active = false
if ( ...unhappy... ) return $.Deferred().reject("unhappy") // abort
if ( polling_active ) initiate_polling() // iterative recursion
})
.fail( r => { polling_active=false, alert('failed: '+r) } ) // report errors
}
This is an elegant approach, but there are some gotchas...
这是一种优雅的方法，但有一些问题......
- If you don't want a
then()to fall through immediately, the callback should return another thenableobject (probably anotherDeferred), which the sleep and ajax lines both do. - The others are too embarrassing to admit. :)
- 如果您不希望 a
then()立即失败，则回调应返回另一个thenable对象（可能是 anotherDeferred）， sleep 和 ajax 行都这样做。 - 其他人都不好意思承认。:)
回答by vaquar khan
(function poll() {
setTimeout(function() {
//
var search = {}
search["ssn"] = "831-33-6049";
search["first"] = "Harve";
search["last"] = "Veum";
search["gender"] = "M";
search["street"] = "5017 Ottis Tunnel Apt. 176";
search["city"] = "Shamrock";
search["state"] = "OK";
search["zip"] = "74068";
search["lat"] = "35.9124";
search["long"] = "-96.578";
search["city_pop"] = "111";
search["job"] = "Higher education careers adviser";
search["dob"] = "1995-08-14";
search["acct_num"] = "11220423";
search["profile"] = "millenials.json";
search["transnum"] = "9999999";
search["transdate"] = $("#datepicker").val();
search["category"] = $("#category").val();
search["amt"] = $("#amt").val();
search["row_key"] = "831-33-6049_9999999";
$.ajax({
type : "POST",
headers : {
contentType : "application/json"
},
contentType : "application/json",
url : "/stream_more",
data : JSON.stringify(search),
dataType : 'json',
complete : poll,
cache : false,
timeout : 600000,
success : function(data) {
//
//alert('jax')
console.log("SUCCESS : ", data);
//$("#btn-search").prop("disabled", false);
// $('#feedback').html("");
for (var i = 0; i < data.length; i++) {
//
$('#feedback').prepend(
'<tr><td>' + data[i].ssn + '</td><td>'
+ data[i].transdate + '</td><td>'
+ data[i].category + '</td><td>'
+ data[i].amt + '</td><td>'
+ data[i].purch_prob + '</td><td>'
+ data[i].offer + '</td></tr>').html();
}
},
error : function(e) {
//alert("error" + e);
var json = "<h4>Ajax Response</h4><pre>" + e.responseText
+ "</pre>";
$('#feedback').html(json);
console.log("ERROR : ", e);
$("#btn-search").prop("disabled", false);
}
});
}, 3000);
})();
回答by Sohan
I created a tiny JQuery plugin for this. You may try it:
我为此创建了一个很小的 JQuery 插件。你可以试试：
$.poll('http://my/url', 100, (xhr, status, data) => {
return data.hello === 'world';
})
回答by jozo
This solution:
这个解决方案：
- has timeout
- polling works also after error response
- 有超时
- 错误响应后轮询也有效
Minimum version of jQuery is 1.12
jQuery 的最低版本是 1.12
$(document).ready(function () {
function poll () {
$.get({
url: '/api/stream/',
success: function (data) {
console.log(data)
},
timeout: 10000 // == 10 seconds timeout
}).always(function () {
setTimeout(poll, 30000) // == 30 seconds polling period
})
}
// start polling
poll()
})
