Run one ajax after another one - javascript

I'm working on the project where I (sadly) cannot use jQuery. And I need to do something which is simple in jQuery but I cannot do it in pure JavaScript. So, I need to run one ajax request using a response form another one. In jQuery it will look like:
$.get("date.php", "", function(data) {
var date=data;
$("#date").load("doku.php?id="+date.replace(" ", "_")+" #to_display", function() {
$(document.createElement("strong")).html(""+date+":").prependTo($(this));
});
});
And this is my code in pure JS which isn't working:
if (window.XMLHttpRequest)
{
ObiektXMLHttp = new XMLHttpRequest();
} else if (window.ActiveXObject)
{
ObiektXMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
if(ObiektXMLHttp)
{
ObiektXMLHttp.open("GET", "date.php");
ObiektXMLHttp.onreadystatechange = function()
{
if (ObiektXMLHttp.readyState == 4)
{
var date = ObiektXMLHttp.responseText;
if (window.XMLHttpRequest)
{
ObiektXMLHttp = new XMLHttpRequest();
} else if (window.ActiveXObject)
{
ObiektXMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
ObiektXMLHttp.open("GET", "doku.php?id="+date.replace(" ", "_"));
ObiektXMLHttp.onreadystatechange = function()
{
if (ObiektXMLHttp.readyState == 4)
{
alert(ObiektXMLHttp.responseText);
}
}
}
}
ObiektXMLHttp.send(null);
}
What am I doing worng?

You forgot to call ObiektXMLHttp.send(null); on second case:
//....
ObiektXMLHttp.open("GET", "doku.php?id="+date.replace(" ", "_"));
ObiektXMLHttp.onreadystatechange = function() {
if (ObiektXMLHttp.readyState == 4)
{
alert(ObiektXMLHttp.responseText);
}
};
//Here
ObiektXMLHttp.send(null);

How about something like this (naive prototype):
// xhr object def
var xhr = {
obj: function() {
if (window.XMLHttpRequest) {
return new XMLHttpRequest();
} else if (window.ActiveXObject) {
return new ActiveXObject("Microsoft.XMLHTTP");
}
throw new Error("can't init xhr object");
},
get: function(url, fn) {
var xhr = this.obj();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
fn(xhr.responseText);
}
};
xhr.open("GET", url);
xhr.send(null);
}
};
// implementation
xhr.get("date.php", function(data){
xhr.get("doku.php?id=" + data.replace(" ", "_"), function(data){
alert(data);
});
});

It's not clear what you got wrong (can you tell us?), but I'd suggest to rely on some helper function like this:
function xhrGet(url, callback) {
if (window.XMLHttpRequest)
var xhr = new XMLHttpRequest();
else if (window.ActiveXObject)
var xhr = new ActiveXObject("Microsoft.XMLHTTP");
if (!xhr) return;
xhr.open("GET", url);
xhr.onreadystatechange = function() {
if (xhr.readyState !== 4) return;
if (typeof callback === "function") callback(xhr);
};
xhr.send(null);
return xhr;
}
So all you have to do is to use this function:
xhrGet("date.php", function(x1) {
xhrGet("doku.php?id=" + date.replace(" ", "_"), function(x2) {
// do stuff
// x1 and x2 are respectively the XHR object of the two requests
});
});

Related

undefined response getting in javascript function ejs

I am trying to get status of any address,in which request_withd function is call ,then action goes on another function named 'is_address_exist' which is return response status of any address in
'yes' or 'no' but i am getting 'undefined' response message in console.
function is_address_exist(address) {
var xmlhttp = new XMLHttpRequest();
var url = '../ withdrawn/address_check/' + address;
xmlhttp.open('GET', url, true);
xmlhttp.send();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState === 4) {
if (xmlhttp.status === 200) {
return xmlhttp.responseText;
}
}
}
}
function request_withd(e) {
var response_status = is_address_exist(address);
console.log(response_status);
}
The onreadystatechange function is a call back function, it runs async, it should have the intended actions included in its definition. This should work.
function is_address_exist(address){
var xmlhttp=new XMLHttpRequest();
var url='../withdrawn/address_check/'+address;
xmlhttp.open('GET',url,true);
xmlhttp.send();
xmlhttp.onreadystatechange=function(){
if(xmlhttp.readyState===4)
{
if(xmlhttp.status===200){
console.log(xmlhttp.responseText);
}
}
}
}
function request_withd(e){
is_address_exist(address);
}
Or for non async function
function is_address_exist(address) {
var responseText ="";
var xmlhttp = new XMLHttpRequest();
var url = '../ withdrawn/address_check/' + address;
xmlhttp.open('GET', url, false);
xmlhttp.send();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState === 4) {
if (xmlhttp.status === 200) {
responseText = xmlhttp.responseText;
}
}
}
return responseText;
}
function request_withd(e) {
var response_status = is_address_exist(address);
console.log(response_status);
}
is_address_exist() doesn't return anything here.
Your return is happening within a xmlhttp.onreadystatechange = () => ...
You could either use callbacks or promises here.
Callback example:
function is_address_exist(address, handler){
//...
xmlhttp.onreadystatechange = function(){
//...
handler(xmlhttp.responseText);
});
}
is_address_exist('...', function(data){
console.log(data);
});
Promise example:
function is_address_exist(){
return new Promise(function (resolve, reject) {
//...
xmlhttp.onreadystatechange = function(){
//...
resolve(xmlhttp.responseText);
});
xmlhttp.onerror = reject;
});
}
is_address_exist()
.then(function (data) {
console.log(data)
})
.catch(console.error.bind(console));

How to make javascript wait until it gets a valid response from synchronous http request?

I know it is not a good idea to use synchronous requests but this is the case that I really need it.
I have tried to make getEndDate function calling to itself if response lenght is less than 20 but after the first unsuccessfull request (if url gives too short response) it goes to alert(enddate.EDDAYOW); and I am getting error, and getEndDate continues sending request every 500 ms.
I need getEndDate function to continue sending a request until it get a valid response and return valid object, and only after that continue to the next line of JS. How to achieve that?
var url = 'http://local.com/cgi-bin/hello2.pl';
// url returns a plain text:
// 1234567890 2013 05 May Friday 13 23 45 01
var enddate = getEndDate(url);
alert(enddate.EDDAYOW);
function getEndDate(url) {
var xmlhttp = getXmlHttp();
xmlhttp.open('GET', url, false);
xmlhttp.send();
if (xmlhttp.status == 200 && xmlhttp.responseText.length > 20) {
var n = xmlhttp.responseText.split(" ");
return {
'edseconds': n[0],
'EDYEAR': n[1],
'EDMON': n[2],
'EDMONNAME': n[3],
'EDDAYOW': n[4],
'EDDAY': n[5],
'EDHOUR': n[6],
'EDMIN': n[7],
'EDSEC': n[8]
};
} else {
setTimeout("getEndDate(" + url + ")", 500);
}
}
function getXmlHttp() {
var xmlhttp;
try {
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
} catch (E) {
xmlhttp = false;
}
}
if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {
xmlhttp = new XMLHttpRequest();
}
return xmlhttp;
}
I don't know if this satisfies your requirement, but I would rewrite it to something like this:
var enddate;
getEndDate(url);
function do_rest(returnDate)
{
enddate = returnDate;
alert(enddate.EDDAYOW);
// do more if you need
};
function getEndDate(url) {
var xmlhttp = getXmlHttp();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
if (xmlhttp.status == 200 && xmlhttp.responseText.length > 20) {
var n = xmlhttp.responseText.split(" ");
do_rest({
'edseconds': n[0],
'EDYEAR': n[1],
'EDMON': n[2],
'EDMONNAME': n[3],
'EDDAYOW': n[4],
'EDDAY': n[5],
'EDHOUR': n[6],
'EDMIN': n[7],
'EDSEC': n[8]
});
} else {
setTimeout("getEndDate(" + url + ")", 500);
}
}
}
xmlhttp.open('GET', url, false);
xmlhttp.send();
}

Getting response from server in javascript

How does I get the response from the server in JavaScript? This is my sample code:
function get_Image(values) {
if (window.XMLHttpRequest) {
var http_request = new XMLHttpRequest();
} else if (window.ActiveXObject) {
var http_request = new ActiveXObject("Microsoft.XMLHTTP");
} else {
http_request.open("GET", "http://sample_address_for_server", true);
http_request.send();
}
alert(http_request.status);
if (http_request.readyState == 4) {
if (http_request.status == 200) {
xmlDoc = http_request.responseText;
alert(xmlDoc);
}
}
}
Try using this block .. the problem with your code is that you missed the quote while creating the open connetion
function get_Image(values){
var http_request = false;
if (window.XMLHttpRequest) {
http_request = new XMLHttpRequest()
} else {
if (window.ActiveXObject) {
try {
http_request = new ActiveXObject("MSXML2.XMLHTTP")
} catch () {
try {
http_request = new ActiveXObject("Microsoft.XMLHTTP")
} catch () {}
}
} else {
return false
}
}
http_request.onreadystatechange = function () {
alert(http_request.status);
if ( http_request.readyState == 4 ) {
if ( http_request.status == 200 ) {
xmlDoc = http_request.responseText;
alert(xmlDoc);
}}
};
http_request.open( "GET", "http://sample_address_for_server", true);
http_request.send(null);
}
you have to attach a function to the object's onreadystatechange event. The way you are doing, you are trying to get the response imediately after you sent the request, you don't have any response yet.
function get_Image(values) {
if (window.XMLHttpRequest) {
var http_request = new XMLHttpRequest();
} else if (window.ActiveXObject) {
var http_request = new ActiveXObject("Microsoft.XMLHTTP");
} else {
http_request.open("GET", "http://sample_address_for_server", true);
http_request.send();
}
alert(http_request.status);
http_request.onreadystatechange = function(){
if (http_request.readyState == 4) {
if (http_request.status == 200) {
xmlDoc = http_request.responseText;
alert(xmlDoc);
}
}
}
}

How can I change this variable with ajax?

I'm curious as to why this isn't working, here's the code:
function Ajax(sUrl, fCallback) {
var url = sUrl || '';
var callback = fCallback || function () {};
var xmlhttp = (function () {
if (window.XMLHttpRequest) {
return new XMLHttpRequest();
} else if (window.ActiveXObject) {
try {
return new ActiveXObject("Msxml2.XMLHTTP.6.0");
} catch (e) {
try {
return new ActiveXObject("Msxml2.XMLHTTP.3.0");
} catch (err) {
return new ActiveXObject("Microsoft.XMLHTTP");
}
}
} else {
return null;
}
}());
this.setUrl = function (newUrl) {
url = newUrl;
};
this.setCallback = function (func) {
callback = func;
};
this.request = function (method, data) {
if (xmlhttp === null) { return false; }
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState === 4) {
callback(xmlhttp.status, xmlhttp.responseXML, xmlhttp.responseText);
}
};
data = data || '';
data = encodeURIComponent(data);
if ((/post/i).test(method)) {
xmlhttp.open('POST', url);
xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xmlhttp.send(data);
} else {
var uri = data === '' ? url : url + '?' + data;
xmlhttp.open('GET', uri);
xmlhttp.send();
}
return true;
};
return this;
}
var ajax = new Ajax(''); // sets the url, not necessary for this demonstration
var changed = false;
function change() {
changed = true;
}
function foo() {
ajax.setCallback(change);
ajax.request();
alert(changed);
}
foo();
There is a fiddle here: http://jsfiddle.net/dTqKG/
I feel like the change function would create a closure that would indeed change the changed variable. Does anyone know what's going on?
The ajax.request(); will return before change() is called. That is the async nature of the AJAX calls, and the reason why you need the callback as opposed to just getting return value from send() method.
Other than that there might be some other issues in the code. I question why wouldn't you use one of the many AJAX frameworks readily available instead of writing your own.

Javascript 2 functions for onClick only run last one

I have a problem using AJAX. The 2 functions that are called via the onclick event, post each value toggle AJAX and back data in two divs. If only put one function in one onclick. it runs well. but put 2, only run the last one ajax2('".$data."','".$num2."');. Where is the problem?
echo "<a OnClick=\"ajax1('".$data."','".$num1."');ajax2('".$data."','".$num2."');\">" click </a>";
two js code, function is similar. just function number, processing page and ruturn div is not same.
function1
function ajax1(data,number) {
HttPRequest = false;
if (window.XMLHttpRequest) {
HttPRequest = new XMLHttpRequest();
if (HttPRequest.overrideMimeType) {
HttPRequest.overrideMimeType('text/html');
}
} else if (window.ActiveXObject) {
try {
HttPRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
HttPRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {}
}
}
}
var url = 'page1.php';
var pmeters = "data=" + data + "&number=" + number;
HttPRequest.open('POST',url,true);
HttPRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
HttPRequest.send(pmeters);
HttPRequest.onreadystatechange = function()
{
if(HttPRequest.readyState == 4)
{
document.getElementById("return1").innerHTML = HttPRequest.responseText;
}
}
}
function2
function ajax2(data,number) {
HttPRequest = false;
if (window.XMLHttpRequest) {
HttPRequest = new XMLHttpRequest();
if (HttPRequest.overrideMimeType) {
HttPRequest.overrideMimeType('text/html');
}
} else if (window.ActiveXObject) {
try {
HttPRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
HttPRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {}
}
}
}
var url = 'page2.php';
var pmeters = "data=" + data + "&number=" + number;
HttPRequest.open('POST',url,true);
HttPRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
HttPRequest.send(pmeters);
HttPRequest.onreadystatechange = function()
{
if(HttPRequest.readyState == 4)
{
document.getElementById("return2").innerHTML = HttPRequest.responseText;
}
}
}
Change the first line of both functions to var HttPRequest = false;. This makes the httprequest private to each function.

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