Develop Reference

How to get new messages using gmail api

I'm writing a Google Chrome browser extension. It uses gmail-api and I want to receive incoming messages coming to the email address of the user who is logged in. How do I implement this in the background script in terms of code. I know that gmail api uses post requests such as watсh, then I don’t know how to implement the code so that I can see messages that would come in real time and my background script would be updated during this event.
My application uses the methods of pull alerts, and accordingly the documentation says that I should use requests such as
https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.subscriptions/pull
https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.subscriptions/acknowledge
How can I use all this in my code so that my script is constantly updated when I receive a new message and is it even possible in javascript?
function POST_request(method,url,_async,params)
{
let xhr= new XMLHttpRequest();
xhr.open(method,url,_async);
xhr.setRequestHeader('Authorization', 'Bearer ' + current_token);
xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
xhr.send(JSON.stringify(params));
return(xhr.responseText);
}
let tmp={
"topicName":"projects/myprofect/topics/mytopic",
"labelFilterAction":"include",
"labelIds": ["INBOX"]
};
console.log(POST_request("POST","https://www.googleapis.com/gmail/v1/users/me/watch",false,tmp));
This query works by returning the view body
{
"historyId": "678576",
"expiration": "1555318376357"
}

XMLHttpRequest receiving undefined

I'm making a widget on iphone but I can't get data from the url.
On IE, I can get data. However, on chrome and on iphone I can't get the data but it only shows undefined instead of data.
function a() {
var url="www.xxx.xxx";
var request = new XMLHttpRequest();
request.open('GET', url, false);
request.send();
xmlDoc = request.responseXML;
}
please help me!! I'm really appreciated for any answers.

Create a function something like below,to receive the data from server.
request.onreadystatechange = function(){
if(request.readyState == 4){
console.log(request.responseText);
}
}

Please make sure that you are making request from the same Origin. That means if you are in site www.abc.com then you can make request for www.abc.com/download/ or www.abc.com/site and so on. But if you request for www.gdb.com then it will probably fail with this error in your console "No 'Access-Control-Allow-Origin' header is present on the requested resource." The browser prevents this activity for security reasons. It needs to be on the same domain.
Try using JQuery sometimes. It's API is very easy to use and is very helpful for doing tasks. You will need to add the script to the page first like this:
<script src="//code.jquery.com/jquery-1.11.2.min.js"></script>
You can download the script or use the live version and link to it like above.
Next you can make a call like this to make a GET request. Observer that it returns data when successful. This makes your job easy but remember you need to make call from same domain.
$.ajax({
type: "GET",
url: "http://wwww.something.com"
})
.done(function( data ) {
alert(data);
})
.fail( function(xhr, textStatus, errorThrown) {
alert(xhr.responseText);
});
To know more about Cross Site HTTP Requests: CORS
Here is a thread that may help you to understand better: “No 'Access-Control-Allow-Origin'

would setting the responseType work?
call the request.responseType = 'document'; before send.

XMLHttpRequest() JSON throws a network error but similar jQuery .getJSON code works

I have a JSON script loaded from an external website. In its simplest form, the code has been like this (and working):
jQuery.getJSON("http://adressesok.posten.no/api/v1/postal_codes.json?postal_code=" + document.querySelector("input").value + "&callback=?",
function(data){
document.querySelector("output").textContent = data.postal_codes[0].city;
});
However, the website owner don't want jQuery if it's not crucial, so I recoded .getJSON to the request = new XMLHttpRequest(); model:
request = new XMLHttpRequest();
request.open("GET", "http://adressesok.posten.no/api/v1/postal_codes.json?postal_code=" + document.querySelector("input").value + "&callback=?", true);
request.onload = function() {
var data = JSON.parse(request.responseText);
document.querySelector("output").textContent = data.postal_codes[0].city;
};
request.onerror = function() { /* this gets called every time */ };
I've modified my code many times, read documentations over and over again, yet the .onerror function is the only one always displaying. This is the console:
Which in Norwegian says that this script requested CORS, that it can't find the origin in the head of Access-Control-Allow-Origin, and that the XMLHttpRequest had a network error, and says "no access".
There could be several reasons as to why this occurs:
1: There's something wrong with the new code
2: There's something in the .getJSON jQuery function (a hack?) that prevents the error from happening
3: There's something crucial in the new code that I have forgot adding
4: There's something with my browser (IE 11 at the moment)
5: Something else?
It would be lovely with some help on this.
DEMO: http://jsbin.com/muxigulegi/1/

That isn't a network error. It's a cross origin error. The request is successful but the browser is denying access to the response to your JavaScript.
Since you have callback=? in the URL, jQuery will generate a JSONP request instead of an XMLHttpRequest request. This executes the response as a script instead of reading the raw data.
You are manually creating an XMLHttpRequest, so it fails due to the Same Origin Policy.
Create a JSONP request instead.

From http://api.jquery.com/jquery.getjson/:
JSONP
If the URL includes the string "callback=?" (or similar, as defined by the server-side API), the request is treated as JSONP instead. See the discussion of the jsonp data type in $.ajax() for more details.
You do have a callback. Which means that the JQuery function can request data from another domain, unlike your XHR call.

Getting Access Denied Error

Getting Access Denied Error on https in IE. while executing ajax call (to my server1) response which has another ajax call While my Ajax call url is on http .By implementing cors I able to execute on http.Tried JSONP also but then it execute my response till it find another ajax call .How to solve ?
below is on myserver1
alert('aaa');
var xhr2 = new XMLHttpRequest();
xhr2.open('GET', 'http://myserver2.com', true);
xhr2.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr2.send();
xhr2.onload = function () {
alert('fff');
var appCreds = xhr2.responseText;
alert(appCreds);
};
alert('xxx');

In addition to the trusted site requirement I found that the problem was not fixed until I used the same protocol for the request as my origin, e.g. my test site was hosted on a https but failed with any destination using http (without the s).
This only applies to IE, Chrome just politely logs a warning in the debug console and doesn't fail.

how to detect a proxy using javascript

in a web page, is there a way to detect by javascript if a web browser is using a PAC file http://xxx.xx.xx.xxx/toto.pac ?
Notes : the same page can be viewd behind many PACs, i don't want to use a server end language, i can edit the toto PAC file if necessary. Regards

You could make an ajax request to a known external server (google.com) and then get the headers out of that request to see if the proxy headers are in the request...
var proxyHeader = 'via';
var req = new XMLHttpRequest();
req.open('GET', document.location, false);
req.send();
var header = req.getResponseHeader(proxyHeader);
if (header) {
// we are on a proxy
}
Change proxyHeader to what ever your proxy adds to the response.
EDIT: You will have to add a conditional for supporting the IE implementation of XMLHttpRequest
EDIT:
I am on a proxy at work and I have just tested this code in jsfiddle and it works. Could be made prettier so that is supports IE and does an async get but the general functionality is there... http://jsfiddle.net/unvHW/
It turns out that detecting 'via' is much better...

Note that this solution will not work on every proxy and would probably only work if you are BEHIND the proxy :
Some proxies append a field in the response headers of an HTTP request which is called : X-Forwarded-For
Maybe you can achieve what you are trying to do with an AJAX request to google.com for example and check if the field is there.
Something like this :
$.ajax({
type: 'POST',
url:'http://www.google.com',
data: formData,
success: function(data, textStatus, request){
if(request.getResponseHeader('X-Forwarded-For')) !== undefined)
alert("Proxy detected !");
}
});
Edit: As Michael said, the X-Forwarded-For is only appended to requests. You'd better check for the response header your proxy puts in the response header.

No.
Browsers do not expose that sort of configuration data to websites.