I was wondering if there is a NON jquery solution to this scenario:
there is no reply to the ajax request because either the server got its internet connection down, the client got its internet connection down, or the server crashed. Is there some built in method/event in the xmlhttprequest object which can help in this issue ?
You can set the timeout property:
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
if (xhr.readyState == 4) {
done(request.responseText);
}
},
done = function (response) { console.log(response) },
fail = function () {};
xhr.open("GET", "url", true);
xhr.timeout = 4000;
xhr.ontimeout = function () { xhr.abort(); fail(); }
xhr.send();
Or just use window.setTimeout
var xhr = new XMLHttpRequest(),
timeout;
xhr.onreadystatechange = function () {
if (xhr.readyState == 4) {
done(request.responseText);
clearTimeout(timeout);
}
};
xhr.open("GET", "url", true);
xhr.timeout = 4000;
xhr.ontimeout = function () { xhr.abort(); fail(); }
xhr.send();
timeout = window.setTimeout(function () { xhr.abort() }, 4000);
Related
I have RestAPI endpoint providing simple response with single flag "needUpdate" true/false.
I am trying to write Javascript polling function which calls this endpoint and in case that needUpdate=true, it reloads whole web page.
var url = "https://www.example.com/api";
var needUpdate;
function poll(){
setTimeout(function(){
const xhr = new XMLHttpRequest();
xhr.open('GET', url);
xhr.responseType = 'json';
xhr.onload = function(e) {
if (this.status == 200) {
const myObj = this.response;
var needUpdate = myObj["needUpdate"];
console.log('needUpdate', needUpdate); // console
}
};
xhr.send();
if(needUpdate == true){
location.reload();
} else {
poll();
}
}, 3000);
}
var json = JSON.stringify(poll());
It calls API every 3 seconds as expected and also states proper value of needUpdate into console. But reload does not happen.
It seems that needUpdate value is actualy undefined on the place where I tried to set a condition.
Can you please help me?
move condition inside xhr.onload function
var url = "https://www.example.com/api";
var needUpdate;
function poll(){
setTimeout(function(){
const xhr = new XMLHttpRequest();
xhr.open('GET', url);
xhr.responseType = 'json';
xhr.onload = function(e) {
if (this.status == 200) {
const myObj = this.response;
var needUpdate = myObj["needUpdate"];
console.log('needUpdate', needUpdate); // console
if(needUpdate == true){
location.reload();
} else {
poll();
}
}
};
xhr.send();
}, 3000);
}
var json = JSON.stringify(poll());
I'm trying to make a script that will return a respond when data is received on the current page. (New Data Received > Log its content to the console)
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == XMLHttpRequest.DONE) {
console.log(xhr.responseText);
}
}
xhr.prototype.open = (function(fopen){
return function(){
console.log("Data received.");
return fopen.apply(this,arguments);
}
})(XMLHttpRequest.prototype.open);
The above script is this script. (source)
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == XMLHttpRequest.DONE) {
console.log(xhr.responseText);
}
}
xhr.open('GET', 'http://example.com', true);
xhr.send(null);
Combine with this script. (source)
XMLHttpRequest.prototype.open = (function(fopen){
return function(){
console.log("Data received.");
return fopen.apply(this,arguments);
}
})(XMLHttpRequest.prototype.open)
I wanted to know what I did wrong and how to make it work. Thanks!
You're assigning to the prototype property of your instantiated object, not to the prototype of XMLHttpRequest. You might want to change XMLHttpRequest.prototype.onreadystatechange instead:
Object.defineProperty(XMLHttpRequest.prototype, 'onreadystatechange', {
set: function(listenerFn) {
this.addEventListener('readystatechange', function(...handlerArgs) {
if (this.readyState == XMLHttpRequest.DONE) {
// Custom action:
// console.log(xhr.responseText);
console.log('Detected a new response');
// Run the previous callback that was passed in:
listenerFn.apply(this, handlerArgs);
}
});
}
});
const xhr = new XMLHttpRequest();
xhr.open('GET', 'https://stacksnippets.net');
xhr.onreadystatechange = () => console.log('handler running');
xhr.send();
This isn't completely in line with the spec of course, this is just an example monkeypatch one might start with. (Mutating the built-in objects like XMLHttpRequest.prototype is bad practice, though - consider avoiding it if possible)
This will log all xhr request
XMLHttpRequest.prototype.send = (function(fsend){
return function(){
this.addEventListener('load', function(){
console.log("Data received.", this.response)
}, {once: true})
return fsend.apply(this, arguments);
}
})(XMLHttpRequest.prototype.send);
xhr = new XMLHttpRequest
xhr.open('GET', 'https://httpbin.org/get')
xhr.send()
hi after searching in the net about how to use the long polling in JavaScript I ended up with three ways, they are mentioned here briefly,but they are implemented using JQuery. I am confused which one to use in case that the AJAX request that I send to the server is asynchronous GET request ,and I don't know how many time it could take.
here is an example AJAX request:
function asynchGETRequest(method,url){
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
console.log("ok");
}
};
xhttp.open(method, url, true);
xhttp.send();
return (xhttp.responseText);
}
var clientFunctions={
getAnswers : function(callback){
var res=asynchGETRequest("GET", "http://localhost:9000/answers");
callback(JSON.stringify(res));
}
}
clientFunctions.getAnswers (function(){
//do some code here after the ajax request is ended
});
can some one guide me please?
I think I found the solution here
function loadFile(sUrl, timeout, callback){
var args = arguments.slice(3);
var xhr = new XMLHttpRequest();
xhr.ontimeout = function () {
console.error("The request for " + url + " timed out.");
};
xhr.onload = function() {
if (xhr.readyState === 4) {
if (xhr.status === 200) {
callback.apply(xhr, args);
} else {
console.error(xhr.statusText);
}
}
};
xhr.open("GET", url, true);
xhr.timeout = timeout;
xhr.send(null);
}
Is it possible for me to call a function then override the contents of the variable before actually running it?
So I have a function that basically pulls in my Git profile like this:
var GetGitInfo = function() {
var xhr = new XMLHttpRequest();
var gitURL = "https://api.github.com/users/myself/repos";
xhr.open("GET", gitURL);
xhr.send(null);
xhr.onreadystatechange = function() {
var DONE = 4; // readyState 4 means the request is done.
var OK = 200; // status 200 is a successful return.
if (xhr.readyState === DONE) {
if (xhr.status === OK) {
// console.log(xhr.responseText);
console.log(JSON.parse(xhr.responseText));
} else {
console.log('Error: ' + xhr.status);
}
}
};
}
Then I call the function in another step by doing GetGitInfo(); which all works fine.
However, If I wanted to call the function and replace the gitURL variable how would I achieve that?
So something like
GetGitInfo(
gotURL= "https://api.github.com/users/new_user/repo";
);
You can't modify a local variable to a function from outside the function. They are private to the function's implementation.
But, since it's your own function, you can just create an argument that can be passed into the function. You can even make the argument optional so it will take your initial value as the default value if it is not passed.
var GetGitInfo = function(url) {
var xhr = new XMLHttpRequest();
var gitURL = url || "https://api.github.com/users/myself/repos";
xhr.open("GET", gitURL);
xhr.send(null);
xhr.onreadystatechange = function() {
var DONE = 4; // readyState 4 means the request is done.
var OK = 200; // status 200 is a successful return.
if (xhr.readyState === DONE) {
if (xhr.status === OK) {
// console.log(xhr.responseText);
console.log(JSON.parse(xhr.responseText));
} else {
console.log('Error: ' + xhr.status);
}
}
};
}
Then, you can use the function the way you were using it or you can pass in an URL to use:
getGitInfo(); // uses your default URL
getGitInfo("http://someURL"); // uses the URL you pass in
FYI, this function looks like it will ultimately need to either return a promise or accept a callback so you can communicate the results back to the caller.
From the snippet above you need to set the url as a function parameter so when calling it uses the specified url.
var GetInfo = function(url) {
var xhr = new XMLHttpRequest();
xhr.open("GET", url);
xhr.send(null);
xhr.onreadystatechange = function() {
var DONE = 4; // readyState 4 means the request is done.
var OK = 200; // status 200 is a successful return.
if (xhr.readyState === DONE) {
if (xhr.status === OK) {
// console.log(xhr.responseText);
console.log(JSON.parse(xhr.responseText));
} else {
console.log('Error: ' + xhr.status);
}
}
};
GetInfo("https://api.github.com/users/myself/repos");
You should do a toString() on the function:
GetGitInfo.toString()
Then you should do a text search and replace on the variable and it's data:
GetGitInfo.toString().substring(0,GetGitInfo.indexOf('somestring'))+'gitUrl="newURL"'+GetGitInfo.toString().substring(.......)
Then you should eval that string!
Or, you know, use function parameters. Either way. Whatever's easiest.
Pass a parameter to the function:
var GetGitInfo = function(gitURL) {
var xhr = new XMLHttpRequest();
xhr.open("GET", gitURL);
xhr.send(null);
xhr.onreadystatechange = function() {
var DONE = 4; // readyState 4 means the request is done.
var OK = 200; // status 200 is a successful return.
if (xhr.readyState === DONE) {
if (xhr.status === OK) {
// console.log(xhr.responseText);
console.log(JSON.parse(xhr.responseText));
} else {
console.log('Error: ' + xhr.status);
}
}
};
}
GetGetInfo("https://api.github.com/users/myself/repos");
Just add a parameter to your function:
var GetGitInfo = function(gitURL) {
var xhr = new XMLHttpRequest();
xhr.open("GET", gitURL);
xhr.send(null);
xhr.onreadystatechange = function() {
var DONE = 4; // readyState 4 means the request is done.
var OK = 200; // status 200 is a successful return.
if (xhr.readyState === DONE) {
if (xhr.status === OK) {
// console.log(xhr.responseText);
console.log(JSON.parse(xhr.responseText));
} else {
console.log('Error: ' + xhr.status);
}
}
};
}
and call it like this:
GetGitInfo("https://api.github.com/users/myself/repos");
Use the parameters
var getData = function(url){
// url can be used here
}
var data = getData("http://apiurl.xy")
I am trying to call an ajax request to my server for json data using a function. If I console out the resp variable inside the ajax function it will show the data successfully. If i try to set the ajax function to a variable, and then console that variable it returns undefined. Any ideas who to make the function request the data and then set ti to a variable to be consoled?
function jsonData(URL) {
var xhr = new XMLHttpRequest();
xhr.open("GET", URL, true);
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
var resp = JSON.parse(xhr.responseText);
return resp;
}
}
xhr.send();
}
jsonString = jsonData(http://mywebsite.com/test.php?data=test);
console.log(jsonString);
This is actually pretty simple.. Change your call to by synchronous..
xhr.open("GET", URL, false);
That being said this will block the browser until the operation has been completed and if you can use a callback instead it would likely be preferred.
function jsonData(URL, cb) {
var xhr = new XMLHttpRequest();
xhr.open("GET", URL, true);
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
var resp = JSON.parse(xhr.responseText);
cb(resp);
}
}
xhr.send();
}
jsonData("http://mywebsite.com/test.php?data=test"
, function(data) { console.log(data); });