I have about 100 ajax requests that I fire at the same time, I thought browsers only allowed a few requests simultaneously, so the rest would be added to a queue.
The problem however is that jquery/javascript seems to use the timeout value from the time the requests were created via jquery, not from the time the requests were actually executed by the browser. So I get a bunch of timeouts. Is it possible to have the timeout start counting from the time the request is actually going to the URI location, instead of the time it is added by jquery?
You may use the timeout settings for ajax request. You may find the jQuery documentation for the same at : http://api.jquery.com/jQuery.ajax/
However the timeout period starts at the point the $.ajax call is made; if several other requests are in progress and the browser has no connections available, it is possible for a request to time out before it can be sent. Therefore you should set some very large value for the timeout if you wish to follow this approach.
A better approach would be to have a local proxy which entertains all the AJAX calls and fires them in a group of 5-10 and then when all these have finished successfully then it fires the next 5-10 requests.
Here is a kind of queue system. Starts by calling the ajax function N times, and then after each success, calls ajax function again. There is also a check in the success callback to see if all the assets have been loaded...
demo fiddle
$(document).ready(function(e) {
$("form[ajax=true]").submit(function(e) {
e.preventDefault();
var form_url = $(this).attr("action");
var form_method = $(this).attr("method").toUpperCase();
$("#loadingimg").show();
var started = 1, done = 0;
function ajax(){
$.ajax({
url: form_url,
type: form_method,
data: "html=started "+(started++),
cache: false,
success: function(returnhtml){
done++;
$("#result").html(returnhtml);
$("#loadingimg").hide();
if(started <= 100){
ajax();
} else if (done == 100) {
alert("all done!");
}
}
});
}
// how many concurrent calls?
for(i=0;i<10;i++){
ajax();
}
});
});
Related
I need to write a setInterval function in javascript. Thi is the code:
var myTimer=setInterval(function(){
var time=0;
$.ajax({
url:'...'
type: "POST",
dataType:"",
success: function (response) {
if(response=="true" || time>=10000){
clearInterval(myTimer);
}
time=time+1000;
},
error: function () {
alert("FAIL");
}
});
},1000);
I don't know why It doesn't stop in clearInterval. Anyone can help me?
You've claimed that the code does "come in the 'if'", so I assume the clearInterval call is actually being made.
Given that, the most likely explanation is that the interval is being cleared (after all, select isn't broken), but before the first "true" response, you've already made more than one ajax call, and the other ones you're seeing are ones scheduled before the interval was cleared.
E.g., your code runs and:
Fires off ajax call #1, which takes more than a second to complete
Fires off ajax call #2
Ajax call #1 completes but isn't "true"
Fires off ajax call #3
Ajax call #2 completes and is "true", clearing the interval
Ajax call #3 completes
Mixing two separate asynchronous intervals (one via setInterval and one via ajax) is asking for trouble.
If the goal is to make the request once a second and stop when you get back "true", I would have the success handler schedule the next call, e.g.:
(function() {
var time = 0;
var started = 0;
start();
function start() {
started = Date.now();
$.ajax({
url: '...'
type: "POST",
dataType: "",
success: function(response) {
if (response != "true") {
// Schedule the next call to occur one second after we
// started the previous call; or almost immediately if
// the call took more than a second to complete
setTimeout(start, Math.max(0, 1000 - (Date.now() - started)));
}
time = time + 1000;
},
error: function() {
alert("FAIL");
}
});
}
})();
Let me illustrate the expected and the actual scenarios to make things clearer.
Scenario #1
The image below shows the case where all your ajax requests complete before one second. You will notice that ajax callback success (or error) functions will execute only before clearInterval (which is what you always expect).
Scenario #2
When some of your ajax requests take more than one second (which is probably what happens), then your ajax callbacks can fire before / after / before-and-after the clearInterval, which makes you feel that your setInterval doesn't stop.
Note that your time variable is useless because it's a function-scoped variable that you initialize to 0 every function call. And even if it's a global variable, it'll only clear the interval in the 11th success function callback, and nothing guarantees how long these 11 successful requests will take.
Solution
As T.J. Crowder suggested, it's better to schedule the next ajax call in the success callback of the previous one, which guarantees that your ajax requests fire sequentially (only one at a time).
Note: Because you edited your question after his answer, then you'll also need to edit the if condition like this:
success: function(response) {
if (response != "true" && time < 10000) {
setTimeout(start, Math.max(0, 1000 - (Date.now() - started)));
}
}
I need to check for a condition and run an AJAX call before sending other AJAX calls on my web app.
I was thinking about putting this AJAX call in a beforeSend on ajaxSetup with async: false (to prevent my initial call from running before this one has completed).
Something like this:
//I set an event that fires:
$.ajax({
type: "GET",
url: my_url,
beforeSend: function() {
//do something, like show a spinner loader gif
}
});
//Somehwere in my app I also have:
$.ajaxSetup({
beforeSend: function() {
if(x===1){
$.ajax({
type: "GET",
url: my_url/fetch_something,
async:false
});
}
}
});
Will my beforeSend on the first AJAX call overrun the one in the ajaxSetup? Is there a way to approach this better?
Better idea of my app:
I have a lot of Ajax calls through the app, each call sends a security hash on the headers to validate the user, these hashes have a time limit as well (both hash and time limit are saved in localStorage)
What I want from ajax setup (and the condition in it) is to check for the time limit - if time_limit < current_time than run an ajax call to refresh the users hash.
This isn't an exercise for 1 or 2 calls, I literally have 20+ growing Ajax calls on my app that make use of the users hash and it's very impractical to make this check in every single one of them.
UPDATED:
Have one method on an interval that sets up the 'session'/local-storage
var refreshing = false;
var intervalID;
$(document).ready(function(e){
var delay = 1234;
intervalID = window.setInterval(setupInterval, delay);
});
function setupInterval(){
refreshing = true;
$.ajax(URL).done(function(r) { //do stuff
setupStorage(r);
refreshing = false;
});
}
function setupStorage(info){
//setup whatever here
}
OLD:
Could you use some logic in your ready function to gate what you need to do?
So basically call one ajax call -> if false, just schedule your latter methods, otherwise run the setup one and on completion schedule the latter method.
Some pseudo-code:
var refresh = false;
$(document).ready(function(e){
$.ajax(URL).done( function(r) {
if(r) {
routeOne();
} else {
latter();
}
});
});
function routeOne(){
$.ajax(URL).done(function(r) { //do stuff
latter();
});
}
function latter(){
//All other ajax calls
}
I'll put some more thought into this let me finish my coffee first...
EDIT:
Based on your updated description could it be possible for you to schedule a setInterval to run the checking method/hash update on the time interval that you need, and is the time interval on your server static or variable? Facebook does this with a heartbeat, I've used this type of logic with some 'locking' functionality in a web-app. If you schedule the interval properly it should not interrupt any other ajax calls.
Try overriding $.ajax to make a "pre-call" before passing in your given query options:
var oldAjax = $.ajax;
$.ajax = function() {
var args = arguments;
oldAjax({
type: "GET",
url: "/echo/html/",
success: function(result){
// do something here to check result
// if result is good, do the request:
return oldAjax.apply($, args);
// if its bad, handle the error
}
});
}
Here's a fiddle to demonstrate: http://jsfiddle.net/NF76U/
I suggest the use of .done() ( $.Deferred object)
function AjaxCall() {
return //code of your ajax without async:false
}
function anotherAjaxCall{
return //code of you ajax call
}
AjaxCall.done(anotherAjaxCall);
Avoid using async:false it's a deprecated practice and it stucks browsers
There is a page and I want periodically to make "background" ajax requests. So the page is loaded then it should send ajax requests in a certain amount of time.
I might use cron for that. I have never use previously so I'm wondering if it would fit for that task. Is there any other more simple way?
P.S. The time delay will be about 5 minutes.
Since there is essentially an unknown delay between the time you send out an AJAX request and the time you receive a complete response for it, an oftentimes more elegant approach is to start the next AJAX call a fixed amount of time after the prior one finishes. This way, you can also ensure that your calls don't overlap.
var set_delay = 5000,
callout = function () {
$.ajax({
/* blah */
})
.done(function (response) {
// update the page
})
.always(function () {
setTimeout(callout, set_delay);
});
};
// initial call
callout();
Cron is run on the serverside and you are using HTML and AJAX, so you should solve this issue in Javascript :-)
By using something like setInterval you can keep executing a function, your case might be something like polling a url via AJAX:
function updatePage(){
// perform AJAX request
}
setInterval(updatePage, 5000);
Depending on your rails version you may be able to use periodically_call_remote, otherwise you'll need the jquery alternative that #Bitterzoet described.
More info in this question.
You can send ajax request in four second like this:
setInterval(get_news, 4000);
function get_news(){
$.ajax('/dashboards/get_news', {
type: 'POST',
success: function(result) {
if(result > 0){
$('#div_1').text("See "+result+" new messages");
$('#div_1').show();
}
else{
$('#div_1').css('display', 'none');
}
},
error: function() {
// alert("Error")
}
});
}
Are you using jquery? If so, you can implement this method:
// first, you need asing a callback timer
var timeout = 300; //milliseconds
// this method contain your ajax request
function ajaxRequest() { //function to ajax request
$.ajax({
url: "/url/to/request/"
}).done(function(data) {
alert("response is: " + data);
});
}
$(document).on("ready", function(){
//this method will be called every 300 milliseconds
setInterval(ajaxRequest, timeout);
});
I'm sending an ajax request to the server on user's input to an <input> element, like this:
$('#my-input').bind("input", function(event){
// here's the ajax request
});
What bothers me is that it send unnecessarily many requests on every user's keyup, meaning that if the user types very fast, there are many unnecessary requests. So I get the idea that there should be a certain delay/timeout, which waits a certain time (50 miliseconds?) for the user to stop typing before sending the ajax request. That would be one problem solved.
But what about cases when the first ajax request haven't been completed before sending another request? (Typing 60 ms / char while ajax request taking 300 ms).
What is the best way to solve this problem (both idea- and code-based)?
You can use throttle function in underscore library. As its documentation says:
Creates and returns a new, throttled version of the passed function, that, when invoked repeatedly, will only actually call the original function at most once per every wait milliseconds. Useful for rate-limiting events that occur faster than you can keep up with.
Even if you don't want to introduce a new library, you can still get idea about how this function works from its source code. In fact, a simple version of throttle function could be:
function throttle(func, delay) {
var timeout = null;
return function() {
var that = this, args = arguments;
clearTimeout(timer);
timeout = setTimeout(function() {
func.apply(that, args);
}, delay);
};
}
This jQuery throttle-debounce plugin is also helpful. Especially, the debounce function seems more suitable to your needs than throttle function according to its author:
Debouncing can be especially useful for rate limiting execution of handlers on events that will trigger AJAX requests
You could just use the setTimeout function. Every so often, see if the text hasn't changed, and if it hasn't, then process accordingly.
setTimeout(function() {
// Do something after 1 second
}, 1000);
You can set async: false in your ajax request so it will process second ajax call only after completion of first ajax request.
I'd go with #HuiZeng's answer, but just in case you want a slightly modified version.
Steps
Listen to keydown using a setTimeout that you can clear.
When it fires, check if you have a previous request in queue, if so abort it and fire a new one
Example:
var inputTimer = 0, req;
function onInput(e){
clearTimeout(inputTImer);
inputTimer = setTimeout( function(){
// You have access to e here
// Cancel any previous requests
req && req.abort();
req = $.ajax({/*...Do your magic here :)*/})
}, 100)
}
I've set up an AJAX page refresh with setInterval.
From time to time, the server is so slow that a new request is initiated before the previous one has completed.
How can I prevent that?
Use a timeout value that is shorter than your refresh interval. When the request times out, it will call the error handler so you'll need to differentiate between time out errors and other types of errors in the handler.
$.ajax({
type: "POST",
url: "some.php",
data: "name=John&location=Boston",
timeout: 5000, /* ms or 5s */
success: function(msg){
alert( "Data Saved: " + msg );
}
});
Docs at jquery.com. Example above from same source, but with added timeout value.
Use setTimeout instead, initiate another setTimeout only after receiving the result of the AJAX request. That way a refresh only happens after the specified period since the last refresh.
Instead of using a fixed, hard coded interval: Trigger the next refresh as the last step of handling the current one, e.g. in the "Success" (or "Complete") event callbacks.
You could add a variable that keeps track of the time the current request was sent, so that you can calculate a dynamic delay:
take current time T1
send asynchronous request
other stuff happens...
asynchronous request returns, callback executes
subtract T1 from current time
if result < your desired request interval, set delay value > 0
if result >= your desired request interval, set delay value = 0
call setTimeout with the delay value, initiating the next cycle
What I can tell you is, use a flag in your code.
Like (not what I actually recommend just a simple example)
var isWorking = false;
function doRequest(){
if(isWorking) return;
isWorking = true;
$.ajax({
...,
success: workWithResponse
});
}
function workWithResponse(){
/* doAnythingelse */
isWorking = false;
}
setInterval(doRequest,1000);
Something like that, its primitive but you will avoid race conditions.
Regards.