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Browser not redirecting to URL

I have an API that returns 302 status code with the destination location.
But when i am calling this API from my angular code, the browser is not redirecting to destination URL. Rather it's calling that destination URL(which is an HTML page) with XHR and giving error like:
error: SyntaxError: Unexpected token < in JSON at position 0 at Object.parse () at XMLHttpRequest.onLoad
text: "\n
Basically it tried parse the HTML response as JSON and failed.
So how can I make browser to redirect to destination URL rather than calling it as XHR.

Browser won't jump to the Location which is returned by XHR 302 response's header. If you want to let the browser redirect, you should make it by your own.
Here is the code:
const url = 'http://your-api.com'
const xhr = new XMLHttpRequest()
xhr.onreadystatechange = () => {
if (xhr.readyState === 4 && xhr.status === 200) {
// This means our request undergoes a redirection
if (xhr.responseURL !== url) {
window.location = xhr.responseURL
}
else {
// Do something else, like JSON.parse(xhr.responseText)
}
}
}
xhr.open('GET', url)
xhr.send()

Javascript HTTP request authentication error

I am trying to call a webservice but I get a authentication error. It is a cross origin request. I have set the 'withcredentials' attribute to manage cross origin requests. But i am still getting the same error.
SOAPClient._loadWsdl = function(url, method, parameters, async, callback)
{
var wsdl = SOAPClient_cacheWsdl[url];
if (wsdl + "" != "" && wsdl + "" != "undefined")
return SOAPClient._sendSoapRequest(url, method, parameters, async, callback, wsdl);
var xmlHttp = SOAPClient._getXmlHttp();
if (SOAPClient.username && SOAPClient.password) {
xmlHttp.open("GET", url + "?wsdl", async, SOAPClient.username, SOAPClient.password);
var auth = "Basic " + SOAPClient._toBase64(SOAPClient.username + ":" + SOAPClient.password);
xmlHttp.withCredentials = true;
//xmlHttp.setRequestHeader( 'Access-Control-Allow-Origin', 'www.website.com');
xmlHttp.setRequestHeader('Authorization', auth);
} else {
xmlHttp.open("GET", url + "?wsdl", async);
}
if (async) {
xmlHttp.onreadystatechange = function() {
alert(xmlHttp.readyState);
if (xmlHttp.readyState == 4)
SOAPClient._onLoadWsdl(url, method, parameters, async, callback, xmlHttp);
}
}
xmlHttp.send(null);
if (!async) `enter code here`
return SOAPClient._onLoadWsdl(url, method, parameters, async, callback, xmlHttp);
}

I suspect this is due to limitations of the browser that won't allow you to do a CORS request. The header would have to be set on the remote server to permit this and it sounds like you don't control it.
Create a server proxy at the domain of the page that can fetch the desired result from the other domain and relay it to you from the allowed domain.
You may want to post the URL of the WDSL server to see if other people can consume it.
p.s.
&& wsdl + "" != "undefined")
This will never evaluate to undefined because you are always concatenating an empty string.

Any way to make AJAX calls to Gmail API without going through JS library?

A simple guide to making a GET request to get a user's messages through Gmail API can be found here.
But the way we are instructed to do the request is in the following manner:
function getMessage(userId, messageId, callback) {
var request = gapi.client.gmail.users.messages.get({
'userId': userId,
'id': messageId
});
request.execute(callback);
}
Is it possible to make the request using the good ol' XMLHttpRequest object on the client side? If so what parameters should be passed into the call?
I have tried this:
var getMessages = function() {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 4 && xhr.status == 200)
console.log(xhr.responseText);
}
xhr.open( "GET", "https://www.googleapis.com/gmail/v1/users/me/messages", true );
xhr.send();
}
But I get a 401, even after authenticating.

As it states in this answer, you should pass the access token as a query parameter with the name access_token, or prefix the authorization header value with "Bearer", like so:
xhr.setRequestHeader("authorization", "Bearer " + userToken.access_token);

catch NS_ERROR_FAILIURE in Firefox

I'm using Topaz Signature pads & implementing their new AJAX library. I want to display a warning on the page if the page if the driver/service is not installed/running. To do this, the script makes a get request to a domain which redirects to localhost via the hosts file.
If the service is running, I get the status of the signature pad & everything is fine. If however, the service is not installed or not running, I just get NS_ERROR_FAILURE and the script halts, even if I'm within try{code}catch(err){errorcode}
try {
console.log('connect: ' + TabletConnectQuery());
}
catch(err){console.log('Caught ' + err);}
My console just shows:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://tablet.sigwebtablet.com:47290/SigWeb/TabletState. (Reason: CORS request failed).
Line 0
NS_ERROR_FAILURE:
https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js line 2 > eval
Line 151
This is particularly troublesome as it occurs during a page transition & stops the animation dead.

I ended up getting it to work by modifying the SigWebTablet.js library topaz provided.
Changed
function SigWebGetProperty(prop) {
var xhr = SigWebcreateXHR();
if (xhr) {
xhr.open("GET", baseUri + prop, false );
xhr.send(null);
if (xhr.readyState == 4 && xhr.status == 200) {
return xhr.responseText;
}
}
return "";
}
To:
function SigWebGetProperty(prop) {
var xhr = SigWebcreateXHR();
if (xhr) {
xhr.open("GET", baseUri + prop, false );
try{
xhr.send(null);
}
catch(err){
return "";
}
if (xhr.readyState == 4 && xhr.status == 200) {
return xhr.responseText;
}
}
return "";
}

Setting up CORS not working

I have the following headers set on the server
response.addHeader("Access-Control-Allow-Origin", "*");
response.addHeader("Access-Control-Allow-Methods", "GET, POST, PUT");
response.addHeader("Access-Control-Allow-Headers","X-Custom-Header");
And i want to use the POST method to access a web service and send data to it but the problem is my setting up with the server is causing problems
I used the following method
function createCORSRequest(method, url) {
var xhr = new XMLHttpRequest();
if ("withCredentials" in xhr) {
// XHR for Chrome/Safari/Firefox.
xhr.open(method, url, true);
}
else if (typeof XDomainRequest != "undefined") {
// XDomainRequest for IE.
xhr = new XDomainRequest();
xhr.open(method, url);
} else {
// CORS not supported.
xhr = null;
}
return xhr;
}
and based on this object
url = "http://myurl.do";
var xhr = createCORSRequest('POST', url);
if (!xhr) {
alert('CORS not supported');
return;
}
var params = "name=pari123&action=initaction&gameId=slotreel3";
xhr.setRequestHeader('Content-Type', 'application/text/plain');
if(xhr.readyState == 4 && xhr.status == 200)
{
alert('Tested OK')
xhr.send(params);
}
else
{
alert('status not 200 or xhr is not ready');
}
// Response handlers.
xhr.onload = function() {
var text = xhr.responseText;
alert('Response from CORS request to ' + url + ': ' + text);
};
xhr.onerror = function() {
alert('Woops, there was an error making the request.');
};
But always it alerts a message saying 'status not 200 or xhr is not ready' i am not able to proceed any one if you know please kindly help!
when i print the xhr.readyState its printing a value of 1

if(xhr.readyState == 4 && xhr.status == 200)
This check must be placed in the onreadystatechange event handler. You obviously cannot have a 200 status code or a "finished" request before actually sending it.
What you wanted is probably this:
xhr.onreadystatechange = function() {
if(xhr.readyState == 4 && xhr.status == 200) {
alert('Tested OK');
var text = xhr.responseText;
alert('Response from CORS request to ' + url + ': ' + text);
}
};
xhr.send(params);
If you want an else case to check for errors remember that you still need to check for xhr.readyState == 4. You don't want your error-handling code to run for other readyStates.
There is no need for the onload event - when you get readyState == 4 you know the request has finished.

There can be several issues here.
I observed that different browsers implement CORS differently. My experience is based on Firefox and Google Chrome. For example, I had to add a special header on server side, so that Firefox would make the preflight (OPTIONS) request and the actual request (GET,PUT etc.) using one connection as Google Chrome does it. You would have to add on the server side:
response.addHeader("Keep-Alive", "timeout=2, max=100");
response.addHeader("Connection", "Keep-Alive");
I also noticed that some browsers do not like the wildcard ("*") in the CORS headers. A workaround for the line
response.addHeader("Access-Control-Allow-Origin", "*");
would be to return the origin of the request and not a wildcard.
However, there could be also other problems and we would need more details. For example, does the request work when the server is hosted on the same domain (i.e. the problem might not be related to CORS). What server are you using?

xhr.send(); needs to be just after the call to xhr.open(); does it not? Status 1 means the request has not been sent yet, it'll never get to status 4 unless you actually send the request..