Develop Reference

Make a while loop delay repeating until ajax calls in it are complete

Before I explain what I want to do, here's an MCV of what I'm coding
$("#button").submit(function(event) {
event.preventDefault();
var formData = new FormData(this);
var myString = $('#textarea').val();
var myRegexp = /src="blob:([^'"]+)"/gm;
match = myRegexp.exec(myString);
var inProgress = 0;
while (match != null) {
var xhr = new XMLHttpRequest();
addr = match[1];
xhr.open('GET', 'blob:' + addr, true);
xhr.responseType = 'blob';
xhr.onload = function(e) {
if (this.status == 200) {
var myBlob = this.response;
var data = new FormData();
data.append('file', myBlob);
$.ajax({
url: "uploader.php",
type: 'POST',
data: data,
contentType: false,
processData: false,
beforeSend: function() {
inProgress++;
},
success: function(data) {
myString = myString.replace("blob:" + addr, data);
},
error: function() {
// error
},
complete: function() {
--inProgress;
}
});
} else {
// error
}
};
xhr.send();
match = myRegexp.exec(myString);
}
if (!inProgress) {
formData.set('textarea', myString);
submitForm(formData);
}
});
So, I have a text area and it contains an unknown number of BLOB objects. I first try to find these BLOB objects using regexp and then I upload them to the server using a PHP file called uploader.php. Once the file is uploaded, it will return the URL of the uploaded file and I want to replace the BLOB URL by the URL of the uploaded file in the text area and then submit the final content of the textarea to the server for further processing.
It turns out that when I run the code, only the last instance of the regexp is replaced by its uploaded URL. The others remain as they were. I suspect that this is because the while loop does not wait for the ajax requests to be complete. I had a similar problem when trying to submit the form and I solved it by following the suggestions in this answer but I don't know how to fix this issue this time.
Any idea is appreciated
Update: I tried to make ajax work synchronously but my browser said that it was deprecated and it didn't work.

It seems you don't really need it to be synchronous (and I can't see a case when it's better to make an async action look synchronous), but rather only need it to be sequential.
It is possible to make async actions sequential by the use of callbacks (which are rewritable as Promise and in turn rewritable as async/await methods but I'll keep it simple):
// myString is made global for simplicity
var myString;
function uploadBlob(myBlob, addr, callback) {
var data = new FormData();
data.append('file', myBlob);
$.ajax({
url: "uploader.php",
type: 'POST',
data: data,
contentType: false,
processData: false,
success: function(data) {
// file uploaded OK, replace the blob expr by the uploaded file url(data)
myString = myString.replace("blob:" + addr, data);
callback();
},
error: function() {
// error, the uploaded most likely failed, we leave myString alone
// or alternatively replace the blob expr by empty string
// because maybe we dont want to post blob in the final form submit
// uncomment if needed
// myString = myString.replace("blob:" + addr, "");
callback();
}
});
}
function getBlobAndUpload(addr, callback) {
var xhr = new XMLHttpRequest();
xhr.open('GET', 'blob:' + addr, true);
xhr.responseType = 'blob';
xhr.onload = function(e) {
if (this.status == 200) {
var myBlob = this.response;
uploadBlob(myBlob, addr, callback);
} else {
// error, but callback anyway to continue processing
callback();
}
};
xhr.send();
}
function processAddresses(addresses, callback, current) {
var index = current || 0;
// all addresses processed?
if (index >= addresses.length) {
// yes no more address, call the callback function
callback();
} else {
var addr = addresses[index];
// once the get/upload is done the next address will be processed
getBlobAndUpload(addr, function() {
processAddresses(addresses, callback, index + 1);
});
}
}
$("#button").submit(function(event) {
event.preventDefault();
var formData = new FormData(this);
var addresses = [];
// initialize both localString and myString to the content of the textArea
// localString will be used to extract addresses,
// while myString will be mutated during the upload process
var localString = myString = $('#textarea').val();
var myRegexp = /src="blob:([^'"]+)"/gm;
match = myRegexp.exec(localString);
// collect all addresses first
while (match != null) {
addr = match[1];
addresses.push(addr);
match = myRegexp.exec(localString);
}
// initiate sequential processing of all addresses, and
// pass the callback function triggering the form submit
processAddresses(addresses, function() {
// all the successfully uploaded blob exprs in my string should
// be now replaced by the remote file url now (see commented part
// in upload blob error for a variation of the feature
formData.set('textarea', myString);
submitForm(formData);
});
});

So. I said in comments, that you could use async/await, and gave links. Now I am going to try to teach you how to work with promises and XMLHttpRequest.
So first thing. I would use my own 'library' (not really a library, just 3 new command) called PromiseReq which has XMLHttpsRequest that returns Promises.
You would need two functions from it:
sendToServer(config, data) and getServerFile(config). They do what their names implies.(sendToServer is not so good at the time, but I will improve it sometime later). They just use Promises as returns. They work in very easy way. Code # Github
BUT It was designed for my uses only, so it is not very flexible (although I hope I will improve it sometime).
So we need to learn how to use Promises.
Firstly you need to know what Promise is and why do we use it.
Then you can create one like this:
let pmq = new Promise((res,rej)=>{
// PROMISE BODY HERE
});
Here first warning. Promises made that way don't support return as a way to resolve Promise! You have to use res()!
Some functions just return them (such as fetch()) and we can handle them right after calling function.
Now pmq will be our promise.
You can use pmq.then(callback) to handle what will happen if somewhere in promise body is res() call and pmq.catch(callback) to handle what happens when rej() is called. Remember, that .catch(cb) and .then(cb) returns a Promise, so you can safely chain more than one .then() and at the end add .catch() and it will handle rejection from every one of .then()s.
For example:
pmq = fetch("file.txt");
pmq.then(e=>console.log(e.json())).then(console.log).catch(console.error);
There is a big note there.
The order in which this events will fire.
If for example rP() waits 1s than logs "A" then resolves, this code:
let a = rP();
a.then(_=>console.log("B")).catch(console.error);
console.log("C");
will result in:
C
A
B
Becuase of this there is async/await needed to do this.
To do so you have to make an async function with keyword async.
let fn = async ()=>{}
Here is second thing. Async functions ALWAYS return Promise. And that is the second way you can create a promise. You just don't use res(), rej() only return and throw.
Now we can call inside fn():
let a = await rP().then(_=>console.log("B")).catch(console.error);
console.log("C");
and we will get our
A
B
C
Now. How to use it with XMLHttpRequest?
You need to create new Promise with simple XMLHttpRequest inside:
let xmlp = (type, path,data) => return new Promise((res,req)=>{
let xhr = new XMLHttpsRequest();
xhr.open(type, path, true); // true implies that is it asynchronous call
//...
xhr.send(data);
});
And now when to resolve?
XMLHttpRequest has useful event properties and events. The one that is best for our case is onreadystatechange.
You can use it like so:
xhr.onreadystatechange = _=>{
if(xhr.readyState === 4 && xhr.status === 200) // Everything went smoothly
res(xhr.responseText);
else if(shr.readyState === 4 && xhr.status !== 200) // Something went wrong!
rej(xhr.status);
}
And then to get data you can either
Async/Await
// INSIDE ASYNC FUNCTION
let resData = await xmpl("GET", "path.txt", null).catch(console.error);
.then()
let resData;
xmpl("GET", "path.txt", null).then(r=>{
resData = r;
// REST OF WHOLE FUNCTION TO ENSURE THAT resData HAS BEEN SET
})
.catch(console.error);
You can also send data with xmpl().
xmpl("POST", "observer.php", "Data to send to observer.php!")
.then(whatToDoAfterSendFN);
/*
to get such data in PHP you have to use
$post = file_get_contents('php://input');
*/
I know that this answer is a bit messy and stuff, but I didn't have any idea how to write it :P Sorry.

XMLHttpRequest - flickr - cross origin header

just having a play with the Flickr API and seem to be unable to successfully claw anything out of it.
I tried using Jquery code below
var flickrURL = "https://api.flickr.com/services/feeds/photos_public.gne?format=jsoncallback=?";
var flickrOptions = {
tags: "cats",
format: "json"
}
var ajaxCallback = function(data){
console.log(data);
};
$.getJSON(flickrURL, flickrOptions, ajaxCallback);
I also tried the old vanilla route
var xhr = new XMLHttpRequest();
xhr.open("GET", "https://api.flickr.com/services/feeds/photos_public.gne?format=jsoncallback=?");
xhr.onreadystatechange = function(data){
console.log(data);
}
xhr.send();
I have used AJAX/XMLrequest successful but not with an API. The when the vanilla fails I'm getting 'No 'Access-Control-Allow-Origin' header' which I don't understand since it's meant to be an open feed and with the Jquery I'm getting 'jsonFlickrFeed is not defined'. Both of which I find very puzzling

Sumeets answer is correct but just thought I'd post my vanilla solution off the back of that.
var script = document.createElement('script');
script.src = "https://api.flickr.com/services/feeds/photos_public.gne?format=json";
document.getElementsByTagName('head')[0].appendChild(script);
var jsonFlickrFeed = function(data){
console.log(data);
}

You just have to do minor changes
var flickrURL =
"https://api.flickr.com/services/feeds/photos_public.gne?format=jsoncallback=?";
var flickrOptions = {
tags: "cats",
format: "json"
}
var jsonFlickrFeed = function(data){
console.log(data);
};
$.getJSON(flickrURL, flickrOptions);
Flickr response looks for jsonFlickrFeed function which was not defined in your case.
https://codepen.io/smtgohil/pen/ZXeYqB?editors=0010
You can check the console for output.

Tableau REST API: Using Javascript to get the Token

I am a complete beginner with REST API and I could not figure out how I am to proceed.
I installed Postman and was successfully able to get the Token, but I am not sure how to send the raw XML payload in javascript.
<tsRequest>
<credentials name ="XXX" password="YYY" >
<site contenturl = "" />
</credentials>
</tsRequest>
I have :
httpRequest.open('POST', 'http://MY-SERVER/api/2.4/auth/signin', false);
httpRequest.setRequestHeader("Content-type", "application/xml");
Not sure how to add the xml payload. I have access to a Tableau Server(MY-SERVER) and everything.
Any help would be greatly appreciated!
Thank you!

You are getting closer, you just need to use the send method to send your XML: https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/send
Just make sure that your XML is properly encoded in javascript when you're inputting it. So if you are using double quotes inside your XML, make sure you have single quotes to declare your string in javascript (e.g.) var data = '<credentials name="XXX" >';
Related: Send POST data using XMLHttpRequest

In addition to #AnilRedshift answer, here's the functioning code:
login_details=[];
function getToken() {
var url = "http://yourServerAddress/api/2.0/auth/signin";
var params = "<tsRequest><credentials name='Username' password='UserPassword' ><site contentUrl='' /></credentials></tsRequest>";
return zuo = new Promise(function(resolve,reject){
var xhr = new XMLHttpRequest();
xhr.open("POST", url, true);
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.withCredentials = true;
xhr.onload= function(){
if (this.status === 200) {
var parsed_xml = JSON.parse(JSON.stringify(x2js.xml_str2json(xhr.responseText)))
login_details.push(parsed_xml.tsResponse.credentials._token); login_details.push(parsed_xml.tsResponse.credentials.site._id);
resolve(login_details);
}
}
xhr.onerror=reject;
xhr.send();
})
}
function getWorkbooks(){
var url = "http://serveraddress//api/2.3/sites/"+login_details[1]+"/workbooks?pageSize=1000";
return zuo = new Promise(function(resolve,reject){
var xhr = new XMLHttpRequest();
xhr.open("GET", url, true);
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.setRequestHeader("X-Tableau-Auth",login_details[0]);
xhr.onload= function(){
if (this.status === 200) {
var workbooks = JSON.parse(JSON.stringify(x2js.xml_str2json(xhr.responseText)))
for (var f=0;f<workbooks.tsResponse.workbooks.workbook.length;f++){
if(workbooks.tsResponse.workbooks.workbook[f].project._name=="Default"){
workbooks_list.push(workbooks.tsResponse.workbooks.workbook[f]._id)
}
resolve();
}
}
}
xhr.onerror= function(){
console.log(xhr.responseText);
}
xhr.send();
})
}
Invoke the code with:
getToken()
.then(function(login_details){
console.log(login_details[0]+"/"+login_details[1]);
})
.then(function(){
getWorkbooks();
})
getToken() function gets the login token which has to be used in all subsequent calls.
getWorkbooks() fetches all dashboards in 'Default' project but this kind of request can be used for all GET type requests.
Please note that this approach uses hardcoded values for password and username which is generally not the best practice. It would be way better to use server side scripting or encrypting (better but still with flavs).
You can find whole step by step tutorial and running code here:
http://meowbi.com/2017/10/23/tableau-fields-definition-undocumented-api/

How can I convert this AJAX request function (raw Javascript) to use POST instead of GET?

I was looking for AJAX in pure JavaScript (without jQuery) for learning purposes and came across this video, along with the code (shown below) on how to make one. However, it's geared towards GET method and I'm not sure how to tweak it to accept additional parameters so that the function can be used for either POST or GET depending on my specified parameters. For example, the lines xhr.open('GET', url, true); and xhr.send(''); both are GET-specific (all other lines in the function are the same for both GET and POST methods)--I want to be able to be able to specify whether to use POST or GET as a parameter for function load for xhr.open and a string such as "username="+username+"&password="+password for function load for xhr.send('');
For example, the function below is for GET and is used like this load('emails.php', function(xhr) {...}. I want the function to be used like this: load('emails.php', 'POST', '"username="+username+"&password="+password' function(xhr) {...}` for POST andload('emails.php', 'GET', '', function(xhr) {...}`
The function for AJAX for GET:
function load(url, callback) {
var xhr;
if(typeof XMLHttpRequest !== 'undefined') xhr = new XMLHttpRequest();
else {
var versions = ["Microsoft.XmlHttp",
"MSXML2.XmlHttp",
"MSXML2.XmlHttp.3.0",
"MSXML2.XmlHttp.4.0",
"MSXML2.XmlHttp.5.0"];
for(var i = 0, len = versions.length; i < len; i++) {
try {
xhr = new ActiveXObject(versions[i]);
break;
}
catch(e){}
} // end for
}
xhr.onreadystatechange = function() {
if((xhr.readyState < 4) || xhr.status !== 200) return;
callback(xhr);
};
xhr.open('GET', url, true);
xhr.send('');
}

Right now the request body is set to null and ignored since you are making a GET request. You should just be able to put whatever you want sent in the body of the POST request inside of the send method:
xhr.open('POST', url, true);
xhr.send(JSON.stringify(someJsonHere));
Check out the documentation for the xhr.send method here:
Here is also a link to a more thorough guide on using XMLHttpRequests; at the bottom it has a section specific to sending data.

Force "charset=x-user-defined'" on jQuery Ajax Post

I am trying to call a Hessian web service from a Javascript application, but I'm having issues parsing the response, since jQuery is treating the response as text and stripping the first bytes of it.
In my research, I have found out that you need to set the charset as 'charset=x-user-defined' in order to the browser leave my bytes as is. But, according the ajax docs:
Sending Data to the Server
By default, Ajax requests are sent using the GET HTTP method. If the
POST method is required, the method can be specified by setting a
value for the type option. This option affects how the contents of the
data option are sent to the server. POST data will always be
transmitted to the server using UTF-8 charset, per the W3C
XMLHTTPRequest standard.
And indeed, the charset is not changing regardless of the settings I used. I have tried the following, separately and all at once, with no luck
$.ajax({
type : 'POST',
url : url,
timeout : 3000,
data : parameters,
contentType : "x-application/hessian; charset=x-user-defined'",
mimeType: 'text/plain; charset=x-user-defined',
headers: {
Accept : "text/plain; charset=x-user-defined",
"Content-Type": "text/plain; charset=x-user-defined"
},
beforeSend : function(xhr) {
xhr.overrideMimeType("text/plain; charset=x-user-defined");
}
})
Also I tried to mess around with the data converters and custom contenttypes defined in jQuery, with no succes.
It appears that as per the standard, I will not be able to do this. It works with GET but not with POST, and the Hessian protocol requires POST.
Do you have any ideas? Or do I need to start to build my XHR method form scratch?

Turns out that I was making a silly mistake somewhere else. But anyhow, I found a sweet way for handling binary data on request and responses, from here.
define(function() {
// Do setup work here
function configurationException(message) {
throw new Error(message + " missing from configuration object");
}
return {
post : function(config) {
if (config) {
var url = config.url || configurationException("url");
var done = config.done || configurationException("callback function");
var timeout = config.timeout || 10000;
var data;
if (config.data) {
data = config.data;
} else {
data = null;
console.warn('No data is specified in binaryPost');
}
var request = new XMLHttpRequest();
request.open("POST", url, true);
request.responseType = "arraybuffer";
request.setRequestHeader("Content-Type", "x-application/hessian;");
request.onload = function(oEvent) {
var arrayBuffer = request.response; // Note: not oReq.responseText
if (arrayBuffer) {
var byteArray = new Uint8Array(arrayBuffer);
done(byteArray);
}
};
request.send(data);
} else {
throw new Error("Configuration object is missing");
}
}
};
});
Hope you find it useful