Develop Reference

Ajax, why the setInterval function doesn't work?

I just have a json page in localhost and I save the data of this page in a file , I need to save this page every 5 seconds, so I developed this code in ajax , using a page in php with an exec command,I used a setinterval function for the update but my code execute the function getRequest only one time.
Here the html:
<script type="text/javascript">
// handles the click event for link 1, sends the query
function getOutput() {
setInterval(function(){
getRequest(
'prova1.php', // URL for the PHP file
drawOutput, // handle successful request
drawError // handle error
);
return false;
},3000);
}
// handles drawing an error message
function drawError() {
var container = document.getElementById('output');
container.innerHTML = 'Bummer: there was an error!';
}
// handles the response, adds the html
function drawOutput(responseText) {
var container = document.getElementById('output');
container.innerHTML = responseText;
}
// helper function for cross-browser request object
function getRequest(url, success, error) {
var req = false;
try{
// most browsers
req = new XMLHttpRequest();
} catch (e){
// IE
try{
req = new ActiveXObject("Msxml2.XMLHTTP");
} catch(e) {
// try an older version
try{
req = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e) {
return false;
}
}
}
if (!req) return false;
if (typeof success != 'function') success = function () {};
if (typeof error!= 'function') error = function () {};
req.onreadystatechange = function(){
if(req.readyState == 4) {
return req.status === 200 ?
success(req.responseText) : error(req.status);
}
}
req.open("GET", url, true);
req.send(null);
return req;
}
</script>
And here the php page:
<?php
exec(" wget http://127.0.0.1:8082/Canvases/Fe0_Cbc1_Calibration/root.json -O provami3.json", $output);
echo 'ok';
?>
I'm new to php , javascript ajax etc and I-m learning it a piece at time, I know that maybe there is an easy way for it using jQuery but for now I'm learning Ajax, so I'd like have an advice for doing it with Ajax.
Thank you all.

Do you have called getOutput() function?I don't see it...
Working example with your code here: http://jsfiddle.net/v9xf1jsw/2/
I've only added this at the end:
getOutput();
Edit:
Working example with getOutput call into a link: http://jsfiddle.net/v9xf1jsw/8/

The JS is fine, see example here counting the loops https://jsfiddle.net/tk9kfdna/1/
<div id="output"></div>
<div id="log"></div>
<script type="text/javascript">
// handles the click event for link 1, sends the query
var times=0;
function getOutput() {
setInterval(function(){
getRequest(
'prova1.php', // URL for the PHP file
drawOutput, // handle successful request
drawError // handle error
);
return false;
},3000);
}
// handles drawing an error message
function drawError() {
var container = document.getElementById('output');
container.innerHTML = 'Bummer: there was an error!';
}
// handles the response, adds the html
function drawOutput(responseText) {
var container = document.getElementById('output');
container.innerHTML = responseText;
}
function getRequest(url, success, error) {
times++;
var req = false;
try{
// most browsers
req = new XMLHttpRequest();
} catch (e){
// IE
try{
req = new ActiveXObject("Msxml2.XMLHTTP");
} catch(e) {
// try an older version
try{
req = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e) {
return false;
}
}
}
if (!req) return false;
if (typeof success != 'function') success = function () {};
if (typeof error!= 'function') error = function () {};
req.onreadystatechange = function(){
if(req.readyState == 4) {
return req.status === 200 ?
success(req.responseText) : error(req.status);
}
}
req.open("GET", url, true);
req.send(null);
var log = document.getElementById('log');
log.innerHTML = 'Loop:'+times;
return req;
}
getOutput();
</script>
Assuming here your calling getOutput() somewhere as that was not included in your original question if not it may just be that. Otherwise what may be happening is a response from prova1.php is never being received and so the script appears like it's not working. The default timeout for XMLHttpRequest request is 0 meaning it will run forever unless you specify the timeout.
Try setting a shorter timeout by adding
req.timeout = 2000; // two seconds
Likely there is an issue with prova1.php? does prova1.php run ok when your try it standalone.

1) Return false at the end of the setInterval method, I don't believe this is necessary.
2) Use a global variable to store the setInterval, (this will also give you the option to cancel the setInterval).
var myInterval;
function getOutput() {
myInterval = setInterval(function(){
getRequest(
'prova1.php', // URL for the PHP file
drawOutput, // handle successful request
drawError // handle error
);
},3000);
}

AJAX and Javascript not working

NO JQUERY. I am using peoplecode which is similar to JSP, ASP, and ZXZ. The ajax request is triggered am I am trying to pull the text 'Hello World' from this script...
Function IScript_AJAX_Test()
%Response.Write("<div id='hello'>Hello World</div>");
End-Function;
My javascript function that makes the ajax call looks like this...
function AJAX_test (ajax_link) {
if (typeof XMLHttpRequest == 'undefined') {
XMLHttpRequest = function() {
try { return new ActiveXObject("Msxml2.XMLHTTP.6.0"); } catch(e) {}
try { return new ActiveXObject("Msxml2.XMLHTTP.3.0"); } catch(e) {}
try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch(e) {}
try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch(e) {}
throw new Error('This browser does not support XMLHttpRequest or XMLHTTP.');
};
}
var request = new XMLHttpRequest();
request.onreadystatechange = function() {
if (request.readyState == 4 && request.status == 200) {
document.getElementById('ajax').innerHTML = request.responseText.document.getElementById('hello').innerHTML;
//document.getElementById('ajax').innerHTML = 'Testing';
}
}
request.open('GET', ajax_link, true);
request.send();
//document.getElementById('ajax').innerHTML = ajax_link;
}
As you can see in this line..
document.getElementById('ajax').innerHTML = request.responseText.document.getElementById('hello').innerHTML;
...I am trying to grab the text by getting the innerHTML from the id. This isn't working though. When I click the button nothing happens.
I tried using the line below, but it returns an entire new page where the id would be (probably because of Peoplesoft)...
document.getElementById('ajax').innerHTML = request.responseText;
Can someone help me achieve this...

I tried your code and it works for me, with
Function IScript_AJAX_Test()
%Response.Write("<div id='hello'>Hello World");
End-Function;
and in the javascript
document.getElementById('ajax').innerHTML = request.responseText;
Make sure you call the content servlet (psc), not the portal servlet (psp), e.g.
'http://peoplesofturl/psc/ps/EMPLOYEE/HRMS/s/WEBLIB_Z_SYS.FUNCLIB.FieldFormula.IScript_AJAX_Test', otherwise you'll get the response wrapped in the peoplesoft portal.
You can generate the url from peoplecode with the GenerateScriptContentRelURL or GenerateScriptContentURL functions.

Make it simple:
Function IScript_AJAX_Test()
%Response.Write("Hello World");
End-Function;
Javascript:
document.getElementById('ajax').innerHTML = request.responseText;

Ajax might be two types. One is server-side and the other one is client-side. You are trying to get data from client side. In this case ajax fetch nothing but the whole page result of a page not a portion. You will have the whole page result(HTML output) if you write
document.getElementById('ajax').innerHTML = request.responseText;
But you cannot fetch just only the innerHtml part of certain portion of another page. On that case you will get the whole page.

Form submit using Ajax

I need to submit the a form using Ajax with POST method.The code is as follows,
function persistPage(divID,url,method){
var scriptId = "inlineScript_" + divID;
var xmlRequest = getXMLHttpRequest();
xmlRequest.open("POST",url,true);
xmlRequest.onreadystatechange = function(){
alert(xmlRequest.readyState + " :" + xmlRequest.status);
if (xmlRequest.readyState ==4 || xmlRequest.status == 200)
document.getElementById(divID).innerHTML=xmlRequest.responseText;
};
xmlRequest.open("POST", url, false);
alert(xmlRequest.readyState);
xmlRequest.send(null);
}
but the form is not submitting(request is not executed or no data posted).How to submit the form using Ajax.
Thanks

There's a few reasons why your code doesn't work. Allow me to break it down and go over the issues one by one. I'll start of with the last (but biggest) problem:
xmlRequest.send(null);
My guess is, you've based your code on a GET example, where the send method is called with null, or even undefined as a parameter (xhr.send()). This is because the url contains the data in a GET request (.php?param1=val1&param2=val2...). When using post, you're going to have to pass the data to the send method.
But Let's not get ahead of ourselves:
function persistPage(divID,url,method)
{
var scriptId = "inlineScript_" + divID;
var xmlRequest = getXMLHttpRequest();//be advised, older IE's don't support this
xmlRequest.open("POST",url,true);
//Set additional headers:
xmlRequest.setRequestHeader('X-Requested-With', 'XMLHttpRequest');//marks ajax request
xmlRequest.setRequestHeader('Content-type', 'application/x-www-form-urlencode');//sending form
The first of the two headers is not always a necessity, but it's better to be safe than sorry, IMO. Now, onward:
xmlRequest.onreadystatechange = function()
{
alert(xmlRequest.readyState + " :" + xmlRequest.status);
if (xmlRequest.readyState ==4 || xmlRequest.status == 200)
document.getElementById(divID).innerHTML=xmlRequest.responseText;
};
This code has a number of issues. You're assigning a method to an object, so there's no need to refer to your object using xmlRequest, though technically valid here, this will break once you move the callback function outside the persistPage function. The xmlRequest variable is local to the function's scope, and cannot be accessed outside it. Besides, as I said before, it's a method: this points to the object directlyYour if statement is a bit weird, too: the readystate must be 4, and status == 200, not or. So:
xmlRequest.onreadystatechange = function()
{
alert(this.readyState + " :" + this.status);
if (this.readyState === 4 && this.status === 200)
{
document.getElementById(divID).innerHTML=this.responseText;
}
};
xmlRequest.open("POST", url, false);
alert(xmlRequest.readyState);//pointless --> ajax is async, so it will alert 0, I think
xmlRequest.send(data);//<-- data goes here
}
How you fill the data is up to you, but make sure the format matches the header: in this case 'content type','x-www-form-urlencode'. Here's a full example of just such a request, it's not exactly a world beater, since I was in the process of ditching jQ in favour of pure JS at the time, but it's serviceable and you might pick up a thing or two. Especially take a closer look at function ajax() definition. In it you'll see a X-browser way to create an xhr-object, and there's a function in there to stringify forms, too
POINTLESS UPDATE:
Just for completeness sake, I'll add a full example:
function getXhr()
{
try
{
return XMLHttpRequest();
}
catch (error)
{
try
{
return new ActiveXObject('Msxml2.XMLHTTP');
}
catch(error)
{
try
{
return new ActiveXObject('Microsoft.XMLHTTP');
}
catch(error)
{
//throw new Error('no Ajax support?');
alert('You have a hopelessly outdated browser');
location.href = 'http://www.mozilla.org/en-US/firefox/';
}
}
}
}
function formalizeObject(form)
{//we'll use this to create our send-data
recursion = recursion || false;
if (typeof form !== 'object')
{
throw new Error('no object provided');
}
var ret = '';
form = form.elements || form;//double check for elements node-list
for (var i=0;i<form.length;i++)
{
if (form[i].type === 'checkbox' || form[i].type === 'radio')
{
if (form[i].checked)
{
ret += (ret.length ? '&' : '') + form[i].name + '=' + form[i].value;
}
continue;
}
ret += (ret.length ? '&' : '') + form[i].name +'='+ form[i].value;
}
return encodeURI(ret);
}
function persistPage(divID,url,method)
{
var scriptId = "inlineScript_" + divID;
var xmlRequest = getXhr();
xmlRequest.open("POST",url,true);
xmlRequest.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
xmlRequest.setRequestHeader('Content-type', 'application/x-www-form-urlencode');
xmlRequest.onreadystatechange = function()
{
alert(this.readyState + " :" + this.status);
if (this.readyState === 4 && this.status === 200)
{
document.getElementById(divID).innerHTML=this.responseText;
}
};
xmlRequest.open("POST", url, false);
alert(xmlRequest.readyState);
xmlRequest.send(formalizeObject(document.getElementById('formId').elements));
}
Just for fun: this code, untested, but should work allright. Though, on each request the persistPage will create a new function object and assign it to the onreadystate event of xmlRequest. You could write this code so that you'll only need to create 1 function. I'm not going into my beloved closures right now (I think you have enough on your plate with this), but it's important to know that functions are objects, and have properties, just like everything else:Replace:
xmlRequest.onreadystatechange = function()
{
alert(this.readyState + " :" + this.status);
if (this.readyState === 4 && this.status === 200)
{
document.getElementById(divID).innerHTML=this.responseText;
}
};
With this:
//inside persistPage function:
xmlRequest.onreadystatechange = formSubmitSuccess;
formSubmitSuccess.divID = divID;//<== assign property to function
//global scope
function formSubmitSuccess()
{
if (this.readyState === 4 && this.status === 200)
{
console.log(this.responseText);
document.getElementById(formSubmitSuccess.divID).innerHTML = this.responseText;
//^^ uses property, set in persistPAge function
}
}
Don't use this though, as async calls could still be running while you're reassigning the property, causing mayhem. If the id is always going to be the same, you can, though (but closures would be even better, then).
Ok, I'll leave it at that

This code can let you understand. The function SendRequest send the request and build the xmlRequest through the GetXMLHttpRequest function
function SendRequest() {
var xmlRequest = GetXMLHttpRequest(),
if(xmlRequest) {
xmlRequest.open("POST", '/urlToPost', true)
xmlRequest.setRequestHeader("connection", "close");
xmlRequest.onreadystatechange = function() {
if (xmlRequest.status == 200) {
// Success
}
else {
// Some errors occured
}
};
xmlRequest.send(null);
}
}
function GetXMLHttpRequest() {
if (navigator.userAgent.indexOf("MSIE") != (-1)) {
var theClass = "Msxml2.XMLHTTP";
if (navigator.appVersion.indexOf("MSIE 5.5") != (-1)) {
theClass = "Microsoft.XMLHTTP";
}
try {
objectXMLHTTP = new ActivexObject(theClass);
return objectXMLHTTP;
}
catch (e) {
alert("Errore: the Activex will not be executed!");
}
}
else if (navigator.userAgent.indexOf("Mozilla") != (-1)) {
objectXMLHTTP = new XMLHttpRequest();
return objectXMLHTTP;
}
else {
alert("!Browser not supported!");
}
}

take a look at this page. In this line: req.send(postData); post data is an array with values that should be posted to server. You have null there. so nothing is posted. You just call request and send no data. In your case you must collect all values from your form, as XMLHTTPRequest is not something that can simply submit form. You must pass all values with JS:
var postData = {};
postData.value1 = document.getElementById("value1id").value;
...
xmlRequest.send(postData);
Where value1 will be available on server like $_POST['value'] (in PHP)
Also there might be a problem with URL or how you are calling persistPage. persistPage code looks ok to me, but maybe I'm missing something. Also you can take a look if you have no errors in console. Press F12 in any browser and find console tab. In FF you may need to install Firebug extention. Also there you will have Network tab with all requests. Open Firebug/Web Inspector(Chrome)/Developer Toolbar(IE) and check if new request is registered in its network tab after you call persistPage.

I found you've invoked the
xmlRequest.open()
method twice, one with async param as true and the other as false. What exactly do you intend to do?
xmlRequest.open("POST", url, true);
...
xmlRequest.open("POST", url, false);
If you want to send asynchronous request, pls pass the param as true.
And also, to use 'POST' method, you'd better send the request header as suggested by Elias,
xmlRequest.setRequestHeader('Content-type', 'application/x-www-form-urlencode');
Otherwise, you may still get unexpected issues.
If you want a synchronous request, actually you may handle the response directly right after you send the request, just like:
xmlRequest.open("POST", url, false);
xmlRequest.send(postData);
// handle response here
document.getElementById(scriptId).innerHTML = xmlRequest.responseText;
Hope this helps.

Ajax response works after two clicks?

I just wrote a basic user-login system where the html page uses javascript to send the ajax request to a servlet which accesses through database.
Here's the js code
var res;
function getXMLObject()
{
var xmlHttp = false;
try {
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP") // For Old Microsoft Browsers
}
catch (e) {
try {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP") // For Microsoft IE 6.0+
}
catch (e2) {
xmlHttp = false // No Browser accepts the XMLHTTP Object then false
}
}
if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
xmlHttp = new XMLHttpRequest(); //For Mozilla, Opera Browsers
}
return xmlHttp; // Mandatory Statement returning the ajax object created
}
var xmlhttp = new getXMLObject(); //xmlhttp holds the ajax object
function handleServerResponse() {
if (xmlhttp.readyState == 4) {
res=xmlhttp.responseText;
}
else {
return false;
alert("Error during AJAX call. Please try again");
}
}
function ajaxFunction() {
var veid=document.getElementById("eid").value;
var vpwd=document.getElementById("pwd").value;
//window.alert('here inside ajaxFunction'+vconf+' '+vseid);
if(xmlhttp) {
xmlhttp.open("GET","check_login?eid="+ veid +"&pwd="+ vpwd,true); //this is the servlet name
xmlhttp.onreadystatechange = handleServerResponse;
xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xmlhttp.send(null);
}
}
function def()
{
//window.alert('hi');
ajaxFunction();
//alert('res:'+res);
if(res=='y')
{
return true;
}
else
{
document.getElementById("uhidden").style.color="#CC0000";
document.getElementById("uhidden").innerHTML="Invalid E-Mail ID or Password"
return false;
}
}
But the code works only after two clicks :(
Any help guys?

Your def function calls ajaxFunction and then straight away checks the res variable. However ajaxFunction just sends the AJAX request; it does not wait for the AJAX response to arrive. Your code is checking the res variable before it is being set from the AJAX response.
This is why it works on the second click - not because the res variable is being set by the second click's AJAX response, but because it is still set from the first click's AJAX response.
The solution is to re-arrange your code a bit. Move the code to display the invalid login message to where the AJAX response is received. In other words, replace the res=xmlhttp.responseText; line with some code to check if xmlhttp.responseText is not y and display the invalid login message.

I guess you call def()
Your Request ist asynchron(because you set the 3rd argument of open() to true ), but in def() you immediately after sending the request work with the the result:
ajaxFunction();
//alert('res:'+res);
if(res=='y')
At this time the request usually is not finished, the result not available yet
Put all code that has to work with the server-response into handleServerResponse()

How can I check existence of a file with JavaScript?

How can I check an existence of a file (It is an xml file that I would like to check in this case) with JavaScript?

if you're using jQuery, you can try to load the file
$.ajax({
type: "GET",
url: "/some.xml",
success: function()
{ /** found! **/},
error: function(xhr, status, error) {
if(xhr.status==404)
{ /** not found! **/}
}
});
if you're not using jQuery:
function ajaxRequest(){
var activexmodes=["Msxml2.XMLHTTP", "Microsoft.XMLHTTP"]
//Test for support for ActiveXObject in IE first (as XMLHttpRequest in IE7 is broken)
if (window.ActiveXObject){
for (var i=0; i<activexmodes.length; i++){
try{
return new ActiveXObject(activexmodes[i])
}
catch(e){
//suppress error
}
}
}
else if (window.XMLHttpRequest) // if Mozilla, Safari etc
return new XMLHttpRequest()
else
return false
}
var myrequest=new ajaxRequest()
myrequest.onreadystatechange=function(){
if (myrequest.readyState==4){ //if request has completed
if (myrequest.status==200 || window.location.href.indexOf("http")==-1){
// FOUND!
}
}
}
myrequest.open('GET', 'http://blabla.com/somefile.xml', true);

If the file is located on the same host that served the page containing the javascript you could try sending an ajax request and verify the returned status code:
function checkFile(fileUrl) {
var xmlHttpReq = false;
var self = this;
// Mozilla/Safari
if (window.XMLHttpRequest) {
self.xmlHttpReq = new XMLHttpRequest();
}
// IE
else if (window.ActiveXObject) {
self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}
self.xmlHttpReq.open('HEAD', fileUrl, true);
self.xmlHttpReq.onreadystatechange = function() {
if (self.xmlHttpReq.readyState == 4) {
if (self.xmlHttpReq.status == 200) {
alert('the file exists');
} else if (self.xmlHttpReq.status == 404) {
alert('the file does not exist');
}
}
}
self.xmlHttpReq.send();
}
checkFile('/somefile.xml');

Javascript doesn't really have any file handling functions. Your best bet is to do the check server side and send some context back to the client.
If you want to get super hacky you COULD call an xmlHttpRequest (If you're using jQuery take a look at the $.ajax function)
Once you call $.ajax you can use the success/error handlers to determine what to do. It should spit out an error if the file doesn't exist.
This of course is NOT a recommended way to do this.

I don't have enough reputation to post comments so let me note that in the Anwar Chandra's answer (non-jQuery version) you have to call eventually:
myrequest.send();
Also, the HEAD method would be better to "check existence of a file", because you don't need to read the whole file from the server.