I'm working on Free Code Camp's wiki viewer and trying to figure out the api call. I thought getjson and ajax were equivalent but maybe i'm doing something wrong.
So at first I used this getjson code:
$.getJSON('http://en.wikipedia.org/w/api.php?action=query&list=search&format=json&srsearch=' + search,
function(api){
console.log(api);
}, 'jsonp');
but it returned this error: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.
Then I used ajax with the same url:
$.ajax({
url: 'http://en.wikipedia.org/w/api.php?action=query&list=search&format=json&srsearch=' + search,
dataType: 'jsonp',
success: getWiki //just console logs the api
});
and this seemed to return the api call. Can anyone explain why getjson didnt work but ajax did?
You're missing the required callback=? query parameter to force $.getJSON to perform a JSONP request
$.getJSON('http://en.wikipedia.org/w/api.php?callback=?', {
action: 'query',
list: 'search',
format: 'json',
srsearch: search
}, api => {
// response handler
})
See http://api.jquery.com/jquery.getjson/#jsonp
This is my solution also I left an alternative using only JavaScript
NOTE I added this &origin=* param in the url to make it work using this the original jQuery code.
var search = 'php';
var searchURL = 'https://en.wikipedia.org/w/api.php?action=query&format=json&generator=search&origin=*&gsrsearch=' + search;
// Using JSON
$.getJSON(searchURL, function(data){
var read = JSON.stringify(data);
console.log('Using jQuery: ' + read);
}, 'jsonp');
// Using JavaScript
var getJSON = function(url, callback) {
var xhr = new XMLHttpRequest();
xhr.open('GET', url, true);
xhr.responseType = 'json';
xhr.onload = function() {
var status = xhr.status;
if (status == 200) {
callback(null, xhr.response);
} else {
callback(status);
}
};
xhr.send();
};
getJSON(searchURL, function(err, data) {
if (err != null) {
alert('Something went wrong: ' + err);
} else {
var read = JSON.stringify(data);
console.log('Using JavaScript: ', read);
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
I have a JavaScript widget which provides standard extension points. One of them is the beforecreate function. It should return false to prevent an item from being created.
I've added an Ajax call into this function using jQuery:
beforecreate: function (node, targetNode, type, to) {
jQuery.get('http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value),
function (result) {
if (result.isOk == false)
alert(result.message);
});
}
But I want to prevent my widget from creating the item, so I should return false in the mother-function, not in the callback. Is there a way to perform a synchronous AJAX request using jQuery or any other in-browser API?
From the jQuery documentation: you specify the asynchronous option to be false to get a synchronous Ajax request. Then your callback can set some data before your mother function proceeds.
Here's what your code would look like if changed as suggested:
beforecreate: function (node, targetNode, type, to) {
jQuery.ajax({
url: 'http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value),
success: function (result) {
if (result.isOk == false) alert(result.message);
},
async: false
});
}
You can put the jQuery's Ajax setup in synchronous mode by calling
jQuery.ajaxSetup({async:false});
And then perform your Ajax calls using jQuery.get( ... );
Then just turning it on again once
jQuery.ajaxSetup({async:true});
I guess it works out the same thing as suggested by #Adam, but it might be helpful to someone that does want to reconfigure their jQuery.get() or jQuery.post() to the more elaborate jQuery.ajax() syntax.
Excellent solution! I noticed when I tried to implement it that if I returned a value in the success clause, it came back as undefined. I had to store it in a variable and return that variable. This is the method I came up with:
function getWhatever() {
// strUrl is whatever URL you need to call
var strUrl = "", strReturn = "";
jQuery.ajax({
url: strUrl,
success: function(html) {
strReturn = html;
},
async:false
});
return strReturn;
}
All of these answers miss the point that doing an Ajax call with async:false will cause the browser to hang until the Ajax request completes. Using a flow control library will solve this problem without hanging up the browser. Here is an example with Frame.js:
beforecreate: function(node,targetNode,type,to) {
Frame(function(next)){
jQuery.get('http://example.com/catalog/create/', next);
});
Frame(function(next, response)){
alert(response);
next();
});
Frame.init();
}
function getURL(url){
return $.ajax({
type: "GET",
url: url,
cache: false,
async: false
}).responseText;
}
//example use
var msg=getURL("message.php");
alert(msg);
Keep in mind that if you're doing a cross-domain Ajax call (by using JSONP) - you can't do it synchronously, the async flag will be ignored by jQuery.
$.ajax({
url: "testserver.php",
dataType: 'jsonp', // jsonp
async: false //IGNORED!!
});
For JSONP-calls you could use:
Ajax-call to your own domain - and do the cross-domain call server-side
Change your code to work asynchronously
Use a "function sequencer" library like Frame.js (this answer)
Block the UI instead of blocking the execution (this answer) (my favourite way)
Note: You shouldn't use async: false due to this warning messages:
Starting with Gecko 30.0 (Firefox 30.0 / Thunderbird 30.0 / SeaMonkey 2.27), synchronous requests on the main thread have been deprecated due to the negative effects to the user experience.
Chrome even warns about this in the console:
Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
This could break your page if you are doing something like this since it could stop working any day.
If you want to do it a way that still feels like if it's synchronous but still don't block then you should use async/await and probably also some ajax that is based on promises like the new Fetch API
async function foo() {
var res = await fetch(url)
console.log(res.ok)
var json = await res.json()
console.log(json)
}
Edit
chrome is working on Disallowing sync XHR in page dismissal when the page is being navigated away or closed by the user. This involves beforeunload, unload, pagehide and visibilitychange.
if this is your use case then you might want to have a look at navigator.sendBeacon instead
It is also possible for the page to disable sync req with either http headers or iframe's allow attribute
I used the answer given by Carcione and modified it to use JSON.
function getUrlJsonSync(url){
var jqxhr = $.ajax({
type: "GET",
url: url,
dataType: 'json',
cache: false,
async: false
});
// 'async' has to be 'false' for this to work
var response = {valid: jqxhr.statusText, data: jqxhr.responseJSON};
return response;
}
function testGetUrlJsonSync()
{
var reply = getUrlJsonSync("myurl");
if (reply.valid == 'OK')
{
console.dir(reply.data);
}
else
{
alert('not valid');
}
}
I added the dataType of 'JSON' and changed the .responseText to responseJSON.
I also retrieved the status using the statusText property of the returned object. Note, that this is the status of the Ajax response, not whether the JSON is valid.
The back-end has to return the response in correct (well-formed) JSON, otherwise the returned object will be undefined.
There are two aspects to consider when answering the original question. One is telling Ajax to perform synchronously (by setting async: false) and the other is returning the response via the calling function's return statement, rather than into a callback function.
I also tried it with POST and it worked.
I changed the GET to POST and added data: postdata
function postUrlJsonSync(url, postdata){
var jqxhr = $.ajax({
type: "POST",
url: url,
data: postdata,
dataType: 'json',
cache: false,
async: false
});
// 'async' has to be 'false' for this to work
var response = {valid: jqxhr.statusText, data: jqxhr.responseJSON};
return response;
}
Note that the above code only works in the case where async is false. If you were to set async: true the returned object jqxhr would not be valid at the time the AJAX call returns, only later when the asynchronous call has finished, but that is much too late to set the response variable.
With async: false you get yourself a blocked browser.
For a non blocking synchronous solution you can use the following:
ES6/ECMAScript2015
With ES6 you can use a generator & the co library:
beforecreate: function (node, targetNode, type, to) {
co(function*(){
let result = yield jQuery.get('http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value));
//Just use the result here
});
}
ES7
With ES7 you can just use asyc await:
beforecreate: function (node, targetNode, type, to) {
(async function(){
let result = await jQuery.get('http://example.com/catalog/create/' + targetNode.id + '?name=' + encode(to.inp[0].value));
//Just use the result here
})();
}
This is example:
$.ajax({
url: "test.html",
async: false
}).done(function(data) {
// Todo something..
}).fail(function(xhr) {
// Todo something..
});
Firstly we should understand when we use $.ajax and when we use $.get/$.post
When we require low level control over the ajax request such as request header settings, caching settings, synchronous settings etc.then we should go for $.ajax.
$.get/$.post: When we do not require low level control over the ajax request.Only simple get/post the data to the server.It is shorthand of
$.ajax({
url: url,
data: data,
success: success,
dataType: dataType
});
and hence we can not use other features(sync,cache etc.) with $.get/$.post.
Hence for low level control(sync,cache,etc.) over ajax request,we should go for $.ajax
$.ajax({
type: 'GET',
url: url,
data: data,
success: success,
dataType: dataType,
async:false
});
this is my simple implementation for ASYNC requests with jQuery. I hope this help anyone.
var queueUrlsForRemove = [
'http://dev-myurl.com/image/1',
'http://dev-myurl.com/image/2',
'http://dev-myurl.com/image/3',
];
var queueImagesDelete = function(){
deleteImage( queueUrlsForRemove.splice(0,1), function(){
if (queueUrlsForRemove.length > 0) {
queueImagesDelete();
}
});
}
var deleteImage = function(url, callback) {
$.ajax({
url: url,
method: 'DELETE'
}).done(function(response){
typeof(callback) == 'function' ? callback(response) : null;
});
}
queueImagesDelete();
Because XMLHttpReponse synchronous operation is deprecated I came up with the following solution that wraps XMLHttpRequest. This allows ordered AJAX queries while still being asycnronous in nature, which is very useful for single use CSRF tokens.
It is also transparent so libraries such as jQuery will operate seamlessly.
/* wrap XMLHttpRequest for synchronous operation */
var XHRQueue = [];
var _XMLHttpRequest = XMLHttpRequest;
XMLHttpRequest = function()
{
var xhr = new _XMLHttpRequest();
var _send = xhr.send;
xhr.send = function()
{
/* queue the request, and if it's the first, process it */
XHRQueue.push([this, arguments]);
if (XHRQueue.length == 1)
this.processQueue();
};
xhr.processQueue = function()
{
var call = XHRQueue[0];
var xhr = call[0];
var args = call[1];
/* you could also set a CSRF token header here */
/* send the request */
_send.apply(xhr, args);
};
xhr.addEventListener('load', function(e)
{
/* you could also retrieve a CSRF token header here */
/* remove the completed request and if there is more, trigger the next */
XHRQueue.shift();
if (XHRQueue.length)
this.processQueue();
});
return xhr;
};
Since the original question was about jQuery.get, it is worth mentioning here that (as mentioned here) one could use async: false in a $.get() but ideally avoid it since asynchronous XMLHTTPRequest is deprecated (and the browser may give a warning):
$.get({
url: url,// mandatory
data: data,
success: success,
dataType: dataType,
async:false // to make it synchronous
});
I have the following jQuery code:
dataString = 'test'; // array?
$.ajax({
type: "POST",
url: "tokenize.php",
data: {
data: dataString
},
cache: false,
success: function (data) {
returnedvalue = data;
console.log(data); //alert isn't for debugging
}
});
This jQuery code is working fine, but I want a plain JavaScript version of this code which I'm not able to figure out how to do. I made up this code with help from Stack Overflow only.
I have seen that this can be done using XMLHttpRequest:
var http = new XMLHttpRequest();
var url = "tokenize.php";
var params = "lorem=ipsum&name=binny"; // What will be done here in my case?
http.open("POST", url, true);
//Send the proper header information along with the request
http.setRequestHeader("Content-length", params.length);
http.setRequestHeader("Connection", "close");
// Call a function when the state changes.
http.onreadystatechange = function () {
if (http.readyState == 4 && http.status == 200) {
alert(http.responseText);
}
}
http.send(params);
The format of application/x-www-form-urlencoded data is:
key=value&key=value&key=value
Run each key and value through encodeURIComponent to deal with characters that have special meaning or that aren't allowed in the encoding.
I am using backbone-tastypie, but I am having the toughest time getting it to work properly. In Tastypie, I am using ApiKeyAuthentication for my resources, so every ajax request, I need to append the apikey and username to the end of a request or send additional headers that add on the username and api key.
I am trying to remove a view and its model using backbone with the following code:
// Remove the goal update view from the DOM
removeItem: function() {
this.model.destroy({wait: true, success: function() {
console.log("success");
}, error: function() {
console.log("error");
}});
},
After the function executes, the browser tries to do a GET request on the following URL:
:8000/api/v1/update/2/
It does not include the api_key or username at the end, and it has a trailing slash at the end of the url. I think it is trying to use Backbone.oldSync to do the GET request. How would I make it so the sync does include the username/api key at the end and removes the trailing slash?
In all of the other requests, I have made it so the api key and username is appended to the end of the http request by adding the following code to backbone-tastypie:
if ( !resp && ( xhr.status === 201 || xhr.status === 202 || xhr.status === 204 ) ) { // 201 CREATED, 202 ACCEPTED or 204 NO CONTENT; response null or empty.
var location = xhr.getResponseHeader( 'Location' ) || model.id;
return $.ajax( {
url: location + "?" + "username=" + window.app.settings.credentials.username + "&api_key=" + window.app.settings.credentials.api_key,
success: dfd.resolve,
error: dfd.reject,
});
}
Let's explore the possibilities
Using headers
Backbone.sync still just uses jQuery ajax so you can override ajaxSend and use headers to send information along.
$(document).ajaxSend(function(e, xhr, options)
{
xhr.setRequestHeader("username", window.app.settings.credentials.username);
xhr.setRequestHeader("api_key", window.app.settings.credentials.api_key);
});
Using Ajax Options
If you need to send the information in just one or two locations, remember that the destroy, fetch, update and save methods are just shortcuts to the ajax caller. So you can add all jQuery ajax parameters to these methods as such:
// Remove the goal update view from the DOM
removeItem: function ()
{
this.model.destroy({
wait: true,
success: function ()
{
console.log("success");
},
error: function ()
{
console.log("error");
},
data:
{
username: window.app.settings.credentials.username,
api_key: window.app.settings.credentials.api_key
}
});
}
Overriding jQuery's ajax method
Depending on your needs, this might be the better implementation (note that this is no production code, you may need to modify this to fit your needs and test this before using it)
(function ($) {
var _ajax = $.ajax;
$.extend(
{
ajax: function (options)
{
var data = options.data || {};
data = _.defaults(data, {
username: window.app.settings.credentials.username,
api_key: window.app.settings.credentials.api_key
});
options.data = data;
return _ajax.call(this, options);
}
});
})(jQuery);
Just for future readers of this post, when you do a model.destroy() you can't pass any data because the delete request doesn't have a body, see this issue for more info:
https://github.com/documentcloud/backbone/issues/789
This question already has answers here:
How should I use servlets and Ajax?
(7 answers)
Closed 7 years ago.
I have a servlet that contains a string, wherein the latter is a JSON string with multiple entries. Now I want to access this String with ajax through jQuery. Now here if my function:
function myFunction() {
$("#myButton").click(function() {
$.ajax({
url: // servlet,
type: "GET",
dataType : "text",
success: function() // I want to display the string from the servlet,
error: // stuff
// other code
Anyway how can I do this. Also can I place another function in the success part rather than an anonymous function?
Is this what you're looking for?
function getString(url, handleResponse, handleFailure) {
var request = new XMLHttpRequest();
request.open("GET", url, true);
request.onload = function () {
if (request.status >= 200 && request.status < 400) {
if (handleResponse) {
handleResponse(request.responseText);
}
} else {
if (handleFailure) {
handleFailure(request.status);
}
}
};
}
this just gets a string from URL (No JQuery)
I want to display the string from the servlet,
your success method has a parameter data
success: function(data){ alert( data ); }
Also can I place another function in the success part rather than an
anonymous function?
success: namedFunction,
function namedFunction(data){ alert(data); }
You can pass function expression to be executed on success or error. First argument for success callback is response sent via server.
Try this:
function successGoesHere(response) {
console.log(response);
}
function errorGoesHere(err) {
console.log(err);
}
function myFunction() {
$("#myButton").click(function() {
$.ajax({
url: "YOUR_URL",
type: "GET",
dataType: "text",
success: successGoesHere,
error: errorGoesHere
})
})
}
As you are passing dataType : "text" in ajax config, response will always be plain text, just in case you are expecting it to be json, your response will be string representation of json hence you will have to parse it using JSON.parse(response) to get JSON object
Use ajax request success : function(resp){
code for parsing json and show parsed json
// var json = $.parseJSON(data);
}
You need to look this
var callback = function(data, textStatus, xhr)
{
alert(data + "\t" + textStatus);
}
var testman = function(str, cb) {
var data = 'Input values';
$.ajax({
type: 'post',
url: '',// servlet
data: data,
success: cb
});
}
testman('Hello, Dear', callback);