I have function getData() which make an ajax call and retrive JSON data. On success i call another function which is marquee() . inside marquee on finish event i call getData() again, But each time getData() when get called, it increases it's request to mentioned file data.php, For example on first call it call once, Second call it request twice, and then twice become 4times,8times and more and more, how to avoid this?!
function getData()
{
$.get('data.php).done(function(response)
{
var data = JSON.parse(response);
if(data.Direction == "left")
{
$(".marquee").html("<span data-direction='"+data.Direction+"'>"+data.Message+"</span>");
}else if(data.Direction == "right"){
$(".marquee").html("<span data- direction='"+data.Direction+"'>"+data.Message+"</span>");
}
});
}
function marquee()
{
$(".marquee").marquee({duration : 10000}).bind("finished",function()
{
getData();
});
}
I hope i was clear... Appreciate each answer.
Every time you are calling marquee function, you are basically binding an event finished on to it. On multiple such function calls, you will have duplicate events. In your code setup, you need to unbind the function before binding it. Something like
$(".marquee").marquee({duration : 10000}).unbind("finished",getData).bind("finished",getData)
Ideally, you should bind only once so you do not have to unbind it again and again.
Related
I'm trying to use the waitFor function of react.js but it seems I'm doing something wrong.
What I want to do i basic, wait for a store to be filled before calling it from another store.
1.Register token in the first store
RipplelinesStore.dispatcherIndex= Dispatcher.register(function(payload) {
var action = payload.action;
var result;
switch(action.actionType) {
case Constants.ActionTypes.ASK_RIPPLELINES:
registerAccount(action.result);
RipplelinesStore.emitChange(action.result);
break;
}
});
2.Write the wait for in the other store
Dispatcher.register(function(payload) {
var action = payload.action;
var result;
switch(action.actionType) {
case Constants.ActionTypes.ASK_RIPPLEACCOUNTOVERVIEW:
console.log("overviewstore",payload);
Dispatcher.waitFor([
RipplelinesStore.dispatcherIndex,
]);
RippleaccountoverviewsStore.test= RipplelinesStore.getAll();
console.log(RippleaccountoverviewsStore.test);
break;
}
return true;
});
Unfortunately my getall() method return an empty object (getAll() is well written). So it seems that the waitFor dispatcher function is not working.
Basically I know that's because the first store is still receiving the answer from the server but I thought that waitFor would waitfor it to be fetched I don't get it.
Any clue ? Thanks!
Edit: I fire the first store fetch like tha. What I don't understand is that I'm dispatching the load once my backbone collection has fetched (I dispatch on succeed with a promise...)
ripplelinescollection.createLinesList(toresolve.toJSON()).then(function() {
Dispatcher.handleViewAction({
actionType: Constants.ActionTypes.ASK_RIPPLELINES,
result: ripplelinescollection
});
});
I also tried to bind the waitfor to an action which is never called but the other store is still not waiting ! WEIRD !
seems like the problem is the async fetch from the server. waitFor isn't supposed to work this way. You will have to introduce another action that is triggered as soon as the data has been received from the server.
Have a look at this answer: https://stackoverflow.com/a/27797444/1717588
Task: get data from server with $.post, process them by method .success(), after that call some function.
var t;
$.when($.post("get_json.php", function(res) {
t = res;
}, 'json')).done(function() {
console.log(t);
});
Do I understand correctly that the Deferred method .done() is executed after .success is done (ie t = res)?
But why "console.log(t)" shows "undefined"?
Is .done() fires after request, but before .success()?
Passing a "success" callback to $.post() is an alternative to the (preferred) chaining of .done(...). Do one or the other, not both, then you don't need to worry about the execution order.
Also, unless you have a decent caching strategy for async data, you shouldn't be setting t as an outer var.
$.post("get_json.php", ...).done(function(t) {
console.log(t);
//do awesome things with t here
});
Caching would be something like this :
var asyncCache = {};
...
function get_t() {
return (asyncCache.t) ? $.when(asyncCache.t) : $.post("get_json.php", ...).done(function(t) {
asyncCache.t = t;
});
}
...
get_t().done(function(t) {
console.log(t);
//do awesome things with t here
}
$.when() is ONLY needed when you have multiple promises and you want to wait for all of them to complete. You simply don't need it at all for your single ajax call. You can just do it like this:
$.post("get_json.php").done(function(t) {
// use the results of the ajax call here
console.log(t);
});
In addition, your code example was using BOTH a success callback function AND a .done() handler. Pick one of the other, not both as they are different ways of getting a callback when the ajax call is done. I'd suggest the promise implementation above because it's more flexible. But, you could also use just the success handler:
$.post("get_json.php", function(t) {
// use the results of the ajax call here
console.log(t);
}, 'json');
Note, when you have an asynchronous operation like this, you need to consume the results of the ajax call in the success callback (or the promise callback) or call some function from there and pass it the data. You do not want to put the data into a global variable or a variable in a higher scope because other code will simply have no way of knowing when the data is ready and when it is not. Put your action in the callback.
If you have more than one ajax call that you want to wait for, then you can do it like this:
$.when($.post("get_json.php"), $.post("get_json2.php")).done(function(r1, r2) {
// use the results of the ajax call here
console.log(r1[0]); // results from first ajax call
console.log(r2[0]); // results from second ajax call
});
Using Knockout 2.0 and MVC3 Razor forms, I am not able to make a dependent observable work when I introduce an ajax method. I have set up a set of observables that are a part of a calculation, and when I return the product of those observables, I am able to set a SPAN tag with the correct result. However, when I try to use the ajax method to handle those observables and return a result, I get unpredictable behavior. First, it appears the ajax POST does not pick up one of the observables when the INPUT fields are updated (var b POSTs to the action method as 0, but then is eventually updated), and then it seems that I am not able to set the result even when it evaluates correctly. It appears there is timing issue with either the observables or the ajax call. Although simply keeping performing the calculation in javascript works fine, my intent is to call ajax methods for more complicated logic. I have removed the call to ko.applybindings from doc.ready(), and also moved the SCRIPT methods to the bottom of the page- this was the only way I found to make this partly functional. My viewModel is set up as follows:
var viewModel = {
a: ko.observable(0),
b: ko.observable(1),
c: ko.observable(2),
// commented this out, since
// the dependent observable will handle this
// d: ko.observable(0)
};
In my dependent observable:
viewModel.d = ko.dependentObservable(function () {
var theResult = 0;
$('.theLabel').css("visibility", "visible");
theResult=viewModel.a() * viewModel.b() * viewModel.c();
// if we return here we get a valid result
return (theResult);
// prefer to call ajax method
// first check to ensure one variable is set
if (viewModel.a() > 0) {
$.ajax("/myCalculation/getResult", {
data: ko.toJSON(viewModel),
type: "post",
context: viewModel,
contentType: "application/json",
success: function (result) {
// can't set visibility here
$('.theLabel').css("visibility", "visible");
// the POST does not pick up some observables, or
// does not the set dependent observable at all
return result;
}
});
}
});
There is quite a bit wrong with the function you have setup.
1.) You are returning from your function before making your AJAX call. The code after your return statement will never execute.
2.) Even if you omit the first return statement, your AJAX call is Asynchronous... which means it will execute in the background and return control to the outer scope immediately. Since you don't have a return statement, then you are going to return undefined.
3.) The comment in your success callback suggests you are expecting the return statement to propagate all the way up to your computed observable. THAT return statement is only scoped to the callback, and not the outer observable. The return value will be used by jQuery, and your observable will long since have returned.
If you want an observable to call an AJAX function you need a seperate value to store the results of the asynchronous call.
Here is a simplified example:
var viewModel = function(){
var $this = this;
$this.a = ko.observable();
$this.b = ko.observable();
$this.results = ko.observable();
//No need to assign this computed observable to a variable
// because the results will be stored in '$this.results'
// we just need this to handle the automatic updates
ko.computed(function(){
var data = {
a: $this.a(),
b: $this.b()
};
$.post("/do/some/stuff", data, function(results){
$this.results(results);
});
});
};
I'm trying to make two Ajax calls to get data to populate different bits of a web page, and as you'll already know, only the second happens.
So I thought I'd do this:
callAjax1('a'); callAjax2('b');
function callAjax1(data) {
ajax(data);
}
function callAjax2(data) {
ajax(data);
}
function ajax(data) {
// calls XMLHttpRequestObject etc
}
The idea was that instead of calling ajax() twice, now, I'd have two independent instances of ajax that would run independently.
It works .. but only if I put in an alert at the top of ajax() to let me know I've arrived.
So I'm thinking that alert gives the first request time to finish before the second is called. Therefore, I've not managed to separate them properly into separate instances. Is that not possible?
What am I missing?
All the best
J
UPDATE:
I'm thinking this, do I stand a chance?
tParams = new Array (2); // we intend to call ajax twice
tParams[0] = new Array('ajaxGetDataController.php', 'PROJECT', 'id');
tParams[1] = new Array('ajaxGetFileController.php', 'FILE', 'projectId');
<select name='projectSelector' onchange=\"saveData(tParams, this.value);\">\n";
// gets called, twice
function saveData(pParams, pData) // pParams are: PageToRun, Table, Field
{
if (XMLHttpRequestObject)
{
tPage = pParams[0][0]+'?table='+pParams[0][1]+'&pField='+pParams[0][2]+'&pData='+pData;
XMLHttpRequestObject.open('GET', tPage);\n
XMLHttpRequestObject.onreadystatechange = callAjax(pParams, pData);
XMLHttpRequestObject.send(null);
}
}
function callAjax(pParams, pData)
{
if (XMLHttpRequestObject.readyState == 4 && XMLHttpRequestObject.status == 200)
{
var tReceived = XMLHttpRequestObject.responseXML;
options = tReceived.getElementsByTagName('option'); // fields and their values stored in simplest XML as options
popForm(options, pParams[0][1]); // goes off to use the DOM to populate the onscreen form
pParams.shift(); // cuts off pParams[0] and moves all elements up one
if (pParams.length>0)
{
saveData(pParams, pData);
}
}
}
I would create a ready state variable for the AJAX function:
function ajax(data) {
readyState = false;
// calls XMLHttpRequestObject etc
}
And then check for the ready state before executing the second call:
function callAjax2(data) {
if(readyState == true) {
ajax(data);
readyState = true;
}
}
And make sure to change the readyState back to false after the AJAX calls have executed. This will ensure the first AJAX call has finished executing before the second one tries to fire.
I've build a livesearch with the jQuery.ajax() method. On every keyup events it receives new result data from the server.
The problem is, when I'm typing very fast, e.g. "foobar" and the GET request of "fooba" requires more time than the "foobar" request, the results of "fooba" are shown.
To handle this with the timeout parameter is impossible, I think.
Has anyone an idea how to solve this?
You can store and .abort() the last request when starting a new one, like this:
var curSearch;
$("#myInput").keyup(function() {
if(curSearch) curSearch.abort(); //cancel previous search
curSearch = $.ajax({ ...ajax options... }); //start a new one, save a reference
});
The $.ajax() method returns the XmlHttpRequest object, so just hang onto it, and when you start the next search, abort the previous one.
Assign a unique, incrementing ID to each request, and only show them in incrementing order. Something like this:
var counter = 0, lastCounter = 0;
function doAjax() {
++counter;
jQuery.ajax(url, function (result) {
if (counter < lastCounter)
return;
lastCounter = counter;
processResult(result);
});
}
You should only start the search when the user hasn't typed anything for a while (500ms or so). This would prevent the problem you're having.
An excellent jQuery plugin which does just that is delayedObserver:
http://code.google.com/p/jquery-utils/wiki/DelayedObserver
Make it so each cancels the last. That might be too much cancellation, but when typing slows, it will trigger.
That seems like an intense amount of traffic to send an ajax request for every KeyUp event. You should wait for the user to stop typing - presumably that they are done, for at least a few 100 milliseconds.
What I would do is this:
var ajaxTimeout;
function doAjax() {
//Your actual ajax request code
}
function keyUpHandler() {
if (ajaxTimeout !== undefined)
clearTimeout(ajaxTimeout);
ajaxTimeout = setTimeout(doAjax, 200);
}
You may have to play with the actual timeout time, but this way works very well and does not require any other plugins.
Edit:
If you need to pass in parameters, create an inline function (closure).
...
var fun = function() { doAjax(params...) };
ajaxTimeout = setTimeout(fun, 200);
You will want some kind of an ajax queue such as:
http://plugins.jquery.com/project/ajaxqueue
or http://www.protofunc.com/scripts/jquery/ajaxManager/
EDIT:Another option, study the Autocomplete plug-in code and emulate that.(there are several Autocomplete as well as the one in jquery UI
OR just implement the Autocomplete if that serves your needs