Handling multithreadiing issue in javascript/jquery? - javascript

$(".getDetails").click(function() {
// some stuff like fetching response from server
})
when user clicks getDetails button on UI multiple times within fraction of second , jquery generates two calls for click function and my logic fails.
I think solution to this will be to disable the button on first click itself(so that use can't click multiple times). Once i get the response or just before returning
from click method i make it enable. Is there any better solution ?
If no, how can i make button disable as soon as user click button first time. I think it needs to be done before calling click method or some where in html element ?
Java provides synchronized keyword so that only one thread enters at time inside method , i am not sure is similar thing exist in javascript or not ?

Assuming the click handler executes an AJAX request you can set the button as disabled before making the request, then enable it again once the request completes. Try this:
$(".getDetails").click(function(){}
var $btn = $(this).prop('disabled', true);
$.ajax({
url: '/foo'
success: function() {
console.log('It worked!');
},
error: function() {
console.log('It failed!');
},
complete: function() {
$btn.prop('disabled', false);
}
});
});

you can try unbinding click event and after ajax call again bind click to that class
$(".getDetails").click(function(){}
$(".getDetails").unbind('click');
// some stuff like fetching response from server
)

You can use simple flag to prevent firing your logic multiple times:
var flag = true
$(".getDetails").click(function() {
if (flag) {
flag = false;
//your logic...
//when your code ends (in after-AJAX callback for example)
flag = true;
}
});

$(".getDetails").click(function(e){
var $target = $(e.currentTarget);
// assuming the click listener is on the button
$target.prop('disabled',true);
// request, stuff...and when done:
$target.prop('disabled',false);
})

try Prevent Default and return false to avoid any other event propagation
This is solution is like semaphore or monitor
var progress = false;
$(".getDetails").on('click', function(e) {
if(!progress){
progress = true;
// some stuff like fetching response from server
//also after sucessfull fetch make true to false again
}else{
console.log('something in progress');
}
e.preventDefault();
return false;
})

This should make sure that your button will not fire the async request twice, until you have a response.
function doAjaxReq() {
/*
Add your ajax operation here
as a return value of doAjaxReq
like so:
return $.ajax({
url: '/foo',
type: 'POST',
data: data
})
Since i can't use ajax here let's smilulate
it useing a promise.
*/
promise = new Promise(function(res, rej) {
setTimeout(function(){
res({foo: "bar"});
}, 1000)
})
return promise;
}
/*
Inside here you add the click handlder
only once use `elem.one('click'...`
*/
function addClickHandler(elem) {
elem.one('click', function() {
// do your ajax request and when its
// done run `addClickHanlder` again
// i'm using `.then` because of the promise,
// you should be using `.done`.
doAjaxReq().then(function(data) {
console.log(data);
addClickHandler(elem);
});
})
}
addClickHandler($(".getDetails"));
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button class="getDetails">Get Details</button>

Related

AJAX on Button Click runs incrementally

I've implemented a simple AJAX call that is bound to a button. On click, the call takes input from an and forwards the value to a FLASK server using getJSON. Using the supplied value (a URL), a request is sent to a website and the html of a website is sent back.
The issue is the AJAX call seems to run multiple times, incrementally depending on how many times it has been clicked.
example;
(click)
1
(click)
2
1
(click)
3
2
1
Because I am sending requests from a FLASK server to another website, it effectively looks like I'm trying to DDOS the server. Any idea how to fix this?
My AJAX code;
var requestNumber = 1; //done for testing purposes
//RUNS PROXY SCRIPT
$("#btnProxy").bind("click", function() . //#btnProxy is the button
{
$.getJSON("/background_process", //background_process is my FLASK route
{txtAddress: $('input[name="Address"]').val(), //Address is the input box
},
console.log(++requestNumber), //increment on function call
function(data)
{$("#web_iframe").attr('srcdoc', data.result); //the FLASK route retrieves the html of a webpage and returns it in an iframe srcdoc.
});
return false;
});
My FLASK code (Though it probably isn't the cause)
#app.route('/background_process')
def background_process():
address = None
try:
address = request.args.get("txtAddress")
resp = requests.get(address)
return jsonify(result=resp.text)
except Exception, e:
return(str(e))
Image of my tested output (I've suppressed the FLASK script)
https://snag.gy/bikCZj.jpg
One of the easiest things to do would be to disable the button after the first click and only enable it after the AJAX call is complete:
var btnProxy = $("#btnProxy");
//RUNS PROXY SCRIPT
btnProxy.bind("click", function () //#btnProxy is the button
{
btnProxy.attr('disabled', 'disabled');//disable the button before the request
$.getJSON("/background_process", //background_process is my FLASK route
{
txtAddress: $('input[name="Address"]').val(), //Address is the input box
},
function (data) {
$("#web_iframe").attr('srcdoc', data.result); //the FLASK route retrieves the html of a webpage and returns it in an iframe srcdoc.
btnProxy.attr('disabled', null);//enable button on success
});
return false;
});
You can try with preventDefault() and see if it fits your needs.
$("#btnProxy").bind("click", function(e) {
e.preventDefault();
$.getJSON("/background_process",
{txtAddress: $('input[name="Address"]').val(),
},
console.log(++requestNumber),
function(data)
{$("#web_iframe").attr('srcdoc', data.result);
});
return false;
});
Probably you are binding the click event multiple times.
$("#btnProxy").bind("click", function() { ... } );
Possible solutions alternatives:
a) Bind the click event only on document load:
$(function() {
$("#btnProxy").bind("click", function() { ... } );
});
b) Use setTimeout and clearTimeout to filter multiple calls:
var to=null;
$("#btnProxy").bind("click", function() {
if(to) clearTimeout(to);
to=setTimeout(function() { ... },500);
});
c) Clear other bindings before set your calls:
$("#btnProxy").off("click");
$("#btnProxy").bind("click", function() { ... } );

Prevent double click of some element

I have a clickable <td> which does some action. However, strange things happen when I quickly make double click. Thus, I want to prevent it and make sure it is only single clickable event.
$.each(response, function(index) {
$('#myID').append('<tr><td onclick="select(this)" >'+ response[index] +'</td></tr>');
});
function select(element){
...
}
I tried to use jQuery's .one() function, but this code above is a product of another event. So, I cannot use $(document).ready(); here. In my knowledge I have to make it like onclick="select(this)"... And it works. But here I need to disable double clicking.
Any help?
So add a check that the Ajax request is active....
function select(element){
var elem = $(element);
if(elem.hasClass("active")) { // is ajax call active?
return false;
}
elem.addClass("active"); // set it that it is active
$.ajax({
url: "foo"
})
.done(function(){})
.always(function(){
elem.removeClass("active"); // call is done, so remove active state
})
}
You can simply disable button until ajax finishes its operation
function select(element){
$(element).prop('disabled', true);
$.ajax({
url'url',
success:function(response){
$(element).prop('disabled', false);
}
});
}

Ajax form is sent twice if validation errors take place

I know about event.preventDefault() and event.stopImmediatePropagation(). But it doesn't work for me. In my case I have such ajax call:
$('#templateConfirmDialog').on('show.bs.modal', function (event) {
$(this).find('.modal-yes').click(function(){
var form = form2js('search_form', '.', true, function (node) {}, false);
var requestData = JSON.stringify(form, replacer);
var $formErrors = $('.search_form').find('.alert-danger');
event.preventDefault();
event.stopImmediatePropagation();
$.ajax({
type: 'POST',
contentType : "application/json",
url: '/fraud/template/testCreate',
data: requestData,
dataType: 'json',
success: function (data) {
$formErrors.text('');
//if no errors just reload
if (data === undefined || data.length === 0) {
location.reload();
}
else {
//else bind error messages
data.forEach(function(error) {
$('#new-' + error.field + '-error').text(error.defaultMessage);
})
}
}
});
});
My problem is that the ajax call is prevented as much times as I made attempts to input data. If I entered invalid data once - ajax is called twice. If twice - 3 times. What may be a reason of such behavior?
Every time this event happens:
$('#templateConfirmDialog').on('show.bs.modal', function (event) {
You bind a new click event handler:
$(this).find('.modal-yes').click(function(){
So if you show.bs.modal twice, then you have two click event handlers both submitting the AJAX request. Instead, just bind the click event handler once to the target clickable element, instead of binding it every time the modal is displayed.
Replace this:
$('#templateConfirmDialog').on('show.bs.modal', function (event) {
$(this).find('.modal-yes').click(function(){
//...
});
});
With this:
$('#templateConfirmDialog').find('.modal-yes').click(function(){
//...
});
Or, if that element is dynamically added to the DOM, this:
$(document).on('click', '#templateConfirmDialog .modal-yes', function(){
//...
});
That way there's just a single click event handler created when the page loads, rather than adding a new handler every time you display the modal.

One button submits AJAX, another button queries result of that AJAX

This question is part of me trying to learn promises and deferreds. Suppose you have a button that submits a POST:
$("#submit").click( function() {
$.post({...})
})
My understanding is that AJAX is itself a promise (which makes obvious sense), so what I'd like to do is, when user clicks #check, it returns the output of the AJAX once it is complete (assuming that #check can and will always be clicked only after #submit has been clicked).
I thought this was simple enough, so my initial code was:
$("#check").click(function() {
$.when($.post({...})).done( function(data) {
console.log("data")
})
})
But I realize that in this implementation, the AJAX wouldn't start POSTing until #check is clicked. There's no need for any #submit button and having the AJAX .post in #submit is redundant.
Is there a way to achieve what I'm doing using promises/deferreds?
Just store the promise returned by post.
var myPromise = null;
$("#submit").click( function() {
myPromise = $.post({...});
});
$("#check").click(function() {
if (myPromise) {
myPromise.then( function(data) {
console.log("data");
});
}
});
The other changes I made are using then() instead of done() (a single function to accept success, failure or progress) and I added statement-ending semicolons (because automatic semicolon insertion kills puppies).
And once you're done studying promises, move on swiftly to observables. With JavaScript the fun never stops.
Based on a comment on the question:
i want to submit something via AJAX, but then i want to use the result of that AJAX ONLY LATER when button check is clicked.
You may be overcomplicating this. You don't really need to dissect the AJAX request/promise/etc. between these two buttons. Simply make the request in the first button and store the result, then use the result in the second button. Something as simple as this:
// disable the check button until there is a result to check
$('#check').prop('disabled', true);
var ajaxResult;
$("#submit").click( function() {
$.post({...})
.done(function (result) {
// any other logic you want to put here, then...
ajaxResult = result;
$('#check').prop('disabled', false);
});
})
$('#check').click(function() {
// the result is in ajaxResult, use it as needed here
});
Basically the "check" button doesn't have anything to do with AJAX. It's just performing an action on data which exists in memory. That button is simply enabled when that data is successfully fetched.
You could create a Promise when the #submit button is pressed, and then use that to establish a handler for the #check button.
$("#submit").click(function() {
var requestPromise = $.post( "xxx", function(response) {
// do something here
})
.fail(function() {
alert( "error" );
})
$("#check").click(function() {
requestPromise.done(function(response) {
// do something meaningful with response here, or other logic
});
// disable #check button and remove click handler here
}
// enable #check button here
})
EDIT - as requested by OP
Here's the version using a compliant Promise:
$("#submit").click(function() {
var requestPromise = new Promise(function(resolve, reject) {
$.post( "xxx", function(response) {
// do something here
resolve(response);
})
.fail(function(response) {
alert( "error" );
reject(response);
});
});
$("#check").click(function() {
requestPromise.then(function(response) {
// do something meaningful with response here, or other logic
});
// disable #check button and remove click handler here
}
// enable #check button here
})

Limit ajaxStart function to only 1 of 2 ajax functions

I have a loading.gif that launches each time the user makes an AJAX powered search. However, I've got some search fields that automatically show suggestions while the user types, also powered by AJAX.
Now my loading.gif appears on the user search as well as the search suggestions while typing. How do I limit my function that shows the loading.gif to only show when it's a user AJAX search and not a search-suggestion-while-typing AJAX search?
This is my function:
$(document).ajaxStart(function () {
$(".se-pre-con").fadeIn("fast");
}).ajaxStop(function () {
$(".se-pre-con").fadeOut("fast");
});
how about bind it with condition like if user is still on the search input then dont show the loading.gif else if the user is out of the search input or first contact on the search input then show the loading.gif (refer below)
first the global variable
var input_focus = false;
and then when the specified input is on focus
$("#specified_input").focus(function(){
//set the variable named 'input_focus' to true to reject the showing of the loader (loading.gif) or hide it.
input_focus = true;
}).blur(function(){
//when the specified input lose it focus then set the variable 'input_focus' to false so that the loader (loading.gif) is allowed to show
input_focus = false;
});
$.ajax({
url : 'my-url',
type : 'post',
data : {},
beforeSend : function(){
//check if input is on focus
if(input_focus !== true){
//show the loading.gif, assume that #loader
$("#loader").show();
}else{
//hide the loading.gif, assume that #loader
$("#loader").hide();
}
},
complete : function(){
//when the ajax request is complete
},
success : function(response){
//the response function
}
});
I'd tackle it by either of the following:
1) Add a global variable such as showLoadingAnimation and set it to true or false depending on the need. Within your ajaxStart and ajaxStop do the following:
$(document).ajaxStart(function () {
if (showLoadingAnimation) $(".se-pre-con").fadeIn("fast");
}).ajaxStop(function () {
if (showLoadingAnimation) $(".se-pre-con").fadeOut("fast");
});
2) Instead of changing the jQuery global settings, Wrap the jQuery method with your own method:
//only listen to ajaxStop event so that we can hide the animation
$(document).ajaxStop(function () {
$(".se-pre-con").fadeOut("fast");
});
function myAjax(params, showAnimation) {
if (showAnimation) $(".se-pre-con").fadeIn("fast");
$.ajax(params);
}
//in your code you instead of calling $.ajax({...}) simply use `myAjax({...})`
Hope this helps.

Categories

Resources