Solution:

If you're not using jQuery in your code, this answer is for you

Your code should be something along the lines of this:

function foo() {
    var httpRequest = new XMLHttpRequest();
    httpRequest.open('GET', "/echo/json");
    httpRequest.send();
    return httpRequest.responseText;
}

var result = foo(); // Always ends up being 'undefined'
Copy code

Felix Kling did a fine job writing an answer for people using jQuery for AJAX, but I've decided to provide an alternative for people who aren't.

(Note, for those using the newfetch API, Angular or promises I've added another answer below)

What you're facing

This is a short summary of "Explanation of the problem" from the other answer, if you're not sure after reading this, read that.

The A in AJAX stands for asynchronous. That means sending the request (or rather receiving the response) is taken out of the normal execution flow. In your example, .send returns immediately and the next statement,return result;, is executed before the function you passed assuccess callback was even called.

This means when you're returning, the listener you've defined did not execute yet, which means the value you're returning has not been defined.

Here is a simple analogy:

function getFive(){
    var a;
    setTimeout(function(){
         a=5;
    },10);
    return a;
}
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(Fiddle)

The value ofa returned isundefined since thea=5 part has not executed yet. AJAX acts like this, you're returning the value before the server got the chance to tell your browser what that value is.

One possible solution to this problem is to code re-actively , telling your program what to do when the calculation completed.

function onComplete(a){ // When the code completes, do this
    alert(a);
}

function getFive(whenDone){
    var a;
    setTimeout(function(){
         a=5;
         whenDone(a);
    },10);
}
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This is called CPS. Basically, we're passinggetFive an action to perform when it completes, we're telling our code how to react when an event completes (like our AJAX call, or in this case the timeout).

Usage would be:

getFive(onComplete);
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Which should alert "5" to the screen. (Fiddle).

Possible solutions

There are basically two ways how to solve this:

1. Make the AJAX call synchronous (let??™s call it SJAX).
2. Restructure your code to work properly with callbacks.

1. Synchronous AJAX - Don't do it!!

As for synchronous AJAX, don't do it! Felix's answer raises some compelling arguments about why it's a bad idea. To sum it up, it'll freeze the user's browser until the server returns the response and create a very bad user experience. Here is another short summary taken from MDN on why:

XMLHttpRequest supports both synchronous and asynchronous communications. In general, however, asynchronous requests should be preferred to synchronous requests for performance reasons.

In short, synchronous requests block the execution of code... ...this can cause serious issues...

If you have to do it, you can pass a flag. Here is how:

var request = new XMLHttpRequest();
request.open('GET', 'yourURL', false);  // `false` makes the request synchronous
request.send(null);

if (request.status === 200) {// That's HTTP for 'ok'
  console.log(request.responseText);
}
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2. Restructure code

Let your function accept a callback. In the example codefoo can be made to accept a callback. We'll be telling our code how to react whenfoo completes.

So:

var result = foo();
// Code that depends on `result` goes here
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Becomes:

foo(function(result) {
    // Code that depends on `result`
});
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Here we passed an anonymous function, but we could just as easily pass a reference to an existing function, making it look like:

function myHandler(result) {
    // Code that depends on `result`
}
foo(myHandler);
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For more details on how this sort of callback design is done, check Felix's answer.

Now, let's define foo itself to act accordingly

function foo(callback) {
    var httpRequest = new XMLHttpRequest();
    httpRequest.onload = function(){ // When the request is loaded
       callback(httpRequest.responseText);// We're calling our method
    };
    httpRequest.open('GET', "/echo/json");
    httpRequest.send();
}
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(fiddle)

We have now made our foo function accept an action to run when the AJAX completes successfully. We can extend this further by checking if the response status is not 200 and acting accordingly (create a fail handler and such). Effectively it is solving our issue.

If you're still having a hard time understanding this, read the AJAX getting started guide at MDN.

Solution:

XMLHttpRequest 2 (first of all, read the answers from Benjamin Gruenbaum and Felix Kling)

If you don't use jQuery and want a nice short XMLHttpRequest 2 which works in the modern browsers and also in the mobile browsers, I suggest to use it this way:

function ajax(a, b, c){ // URL, callback, just a placeholder
  c = new XMLHttpRequest;
  c.open('GET', a);
  c.onload = b;
  c.send()
}
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As you can see:

1. It's shorter than all other functions Listed.
2. The callback is set directly (so no extra unnecessary closures).
3. It uses the new onload (so you don't have to check for readystate && status)
4. There are some other situations, which I don't remember, that make the XMLHttpRequest 1 annoying.

There are two ways to get the response of this Ajax call (three using the XMLHttpRequest var name):

The simplest:

this.response
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Or if for some reason youbind() the callback to a class:

e.target.response
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Example:

function callback(e){
  console.log(this.response);
}
ajax('URL', callback);
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Or (the above one is better anonymous functions are always a problem):

ajax('URL', function(e){console.log(this.response)});
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Nothing easier.

Now some people will probably say that it's better to use onreadystatechange or the even the XMLHttpRequest variable name. That's wrong.

Check out XMLHttpRequest advanced features.

It supported all *modern browsers. And I can confirm as I have been using this approach since XMLHttpRequest 2 was created. I never had any type of problem in any browsers I used.

onreadystatechange is only useful if you want to get the headers on state 2.

Using theXMLHttpRequest variable name is another big error as you need to execute the callback inside the onload/oreadystatechange closures, or else you lost it.

Now if you want something more complex using POST and FormData you can easily extend this function:

function x(a, b, e, d, c){ // URL, callback, method, formdata or {key:val},placeholder
  c = new XMLHttpRequest;
  c.open(e||'get', a);
  c.onload = b;
  c.send(d||null)
}
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Again ... it's a very short function, but it does GET and POST.

Examples of usage:

x(url, callback); // By default it's GET so no need to set
x(url, callback, 'post', {'key': 'val'}); // No need to set POST data
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Or pass a full form element (document.getElementsByTagName('form')[0]):

var fd = new FormData(form);
x(url, callback, 'post', fd);
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Or set some custom values:

var fd = new FormData();
fd.append('key', 'val')
x(url, callback, 'post', fd);
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As you can see, I didn't implement sync... it's a bad thing.

Having said that ... why don't we do it the easy way?

As mentioned in the comment, the use of error && synchronous does completely break the point of the answer. Which is a nice short way to use Ajax in the proper way?

Error handler

function x(a, b, e, d, c){ // URL, callback, method, formdata or {key:val}, placeholder
  c = new XMLHttpRequest;
  c.open(e||'get', a);
  c.onload = b;
  c.onerror = error;
  c.send(d||null)
}

function error(e){
  console.log('--Error--', this.type);
  console.log('this: ', this);
  console.log('Event: ', e)
}
function displayAjax(e){
  console.log(e, this);
}
x('WRONGURL', displayAjax);
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In the above script, you have an error handler which is statically defined, so it does not compromise the function. The error handler can be used for other functions too.

But to really get out an error, the only way is to write a wrong URL in which case every browser throws an error.

Error handlers are maybe useful if you set custom headers, set the responseType to blob array buffer, or whatever...

Even if you pass 'POSTAPAPAP' as the method it won't throw an error.

Even if you pass 'fdggdgilfdghfldj' as formdata it won't throw an error.

In the first case the error is inside thedisplayAjax() underthis.statusText asMethod not Allowed.

In the second case, it simply works. You have to check at the server side if you passed the right post data.

Cross-domain not allowed throws an error automatically.

In the error response, there aren't any error codes.

There is only thethis.type which is set to error.

Why add an error handler if you totally don't have any control over errors? Most of the errors are returned inside this in the callback functiondisplayAjax().

So: There isn't any need for error checks if you're able to copy and paste the URL properly. ;)

PS: As the first test I wrote x('x', displayAjax)..., and it totally got a response...??? So I checked the folder where the HTML is located, and there was a file called 'x.xml'. So even if you forget the extension of your file XMLHttpRequest 2 WILL FIND IT. I LOL'd

Read a file synchronous

Don't do that.

If you want to block the browser for a while load a nice big.txt file synchronous.

function omg(a, c){ // URL
  c = new XMLHttpRequest;
  c.open('GET', a, true);
  c.send();
  return c; // Or c.response
}
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Now you can do

 var res = omg('thisIsGonnaBlockThePage.txt');
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There is no other way to do this in a non-asynchronous way. (Yeah, with setTimeout loop... but seriously?)

Another point is... if you work with APIs or just your own list's files or whatever you always use different functions for each request...

Only if you have a page where you load always the same XML/JSON or whatever you need only one function. In that case, modify a little the Ajax function and replace b with your special function.

The functions above are for basic use.

If you want to extend the function...

Yes, you can.

I'm using a lot of APIs and one of the first functions I integrate into every HTML page is the first Ajax function in this answer, with GET only...

But you can do a lot of stuff with XMLHttpRequest 2:

I made a download manager (using ranges on both sides with resume, filereader, and filesystem), various image resizers converters using canvas, populate web SQL databases with base64images and much more...

But in these cases you should create a function only for that purpose... sometimes you need a blob, array buffers, you can set headers, override mimetype and there is a lot more...

But the question here is how to return an Ajax response... (I added an easy way.)

Solution:

If you're using promises, this answer is for you.

This means AngularJS, jQuery (with deferred), native XHR's replacement (fetch), Ember.js, Backbone.js's save or any Node.js library that returns promises.

Your code should be something along the lines of this:

function foo() {
    var data;
    // Or $.get(...).then, or request(...).then, or query(...).then
    fetch("/echo/json").then(function(response){
        data = response.json();
    });
    return data;
}

var result = foo(); // 'result' is always undefined no matter what.
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Felix Kling did a fine job writing an answer for people using jQuery with callbacks for Ajax. I have an answer for native XHR. This answer is for generic usage of promises either on the frontend or backend.

The core issue

The JavaScript concurrency model in the browser and on the server with Node.js/io.js is asynchronous and reactive.

Whenever you call a method that returns a promise, thethen handlers are always executed asynchronously - that is, after the code below them that is not in a.then handler.

This means when you're returningdata thethen handler you've defined did not execute yet. This in turn means that the value you're returning has not been set to the correct value in time.

Here is a simple analogy for the issue:

    function getFive(){
        var data;
        setTimeout(function(){ // Set a timer for one second in the future
           data = 5; // After a second, do this
        }, 1000);
        return data;
    }
    document.body.innerHTML = getFive(); // `undefined` here and not 5Copy code

function handleData( responseData ) {

    // Do what you want with the data
    console.log(responseData);
}

$.ajax({
    url: "hi.php",
    ...
    success: function ( data, status, XHR ) {
        handleData(data);
    }
});
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function callServerAsync(){
    $.ajax({
        url: '...',
        success: function(response) {

            successCallback(response);
        }
    });
}

function successCallback(responseObj){
    // Do something like read the response and show data
    alert(JSON.stringify(responseObj)); // Only applicable to a JSON response
}

function foo(callback) {

    $.ajax({
        url: '...',
        success: function(response) {
           return callback(null, response);
        }
    });
}

var result = foo(function(err, result){
          if (!err)
           console.log(result);
});
Copy code

  promiseB = promiseA.then(
    function onSuccess(result) {
      return result + 1;
    }
    ,function onError(err) {
      // Handle error
    }
  );

 // promiseB will be resolved immediately after promiseA is resolved
 // and its value will be the result of promiseA incremented by 1.
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 search(term: string) {
     return this.http
       .get(`https://api.spotify.com/v1/search?q=${term}&type=artist`)
       .map((response) => response.json())
       .toPromise();
}
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search() {
    this.searchService.search(this.searchField.value)
      .then((result) => {
    this.result = result.artists.items;
  })
  .catch((error) => console.error(error));
}
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465

votes

Answer

Solution:

Most of the answers here give useful suggestions for when you have a single async operation, but sometimes, this comes up when you need to do an asynchronous operation for each entry in an array or other list-like structure. The temptation is to do this:

// WRONG
var results = [];
theArray.forEach(function(entry) {
    doSomethingAsync(entry, function(result) {
        results.push(result);
    });
});
console.log(results); // E.g., using them, returning them, etc.
Copy code

Example:

// WRONG
var theArray = [1, 2, 3];
var results = [];
theArray.forEach(function(entry) {
    doSomethingAsync(entry, function(result) {
        results.push(result);
    });
});
console.log("Results:", results); // E.g., using them, returning them, etc.

function doSomethingAsync(value, callback) {
    console.log("Starting async operation for " + value);
    setTimeout(function() {
        console.log("Completing async operation for " + value);
        callback(value * 2);
    }, Math.floor(Math.random() * 200));
}Copy code

.as-console-wrapper { max-height: 100% !important; }Copy code

Undefined answered

2022-05-18

Link to answer

---

---

993

votes

Answer

Solution:

Have a look at this example:

var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope,$http) {

    var getJoke = function(){
        return $http.get('http://api.icndb.com/jokes/random').then(function(res){
            return res.data.value;  
        });
    }

    getJoke().then(function(res) {
        console.log(res.joke);
    });
});
Copy code

As you can seegetJoke is returning a resolved promise (it is resolved when returningres.data.value). So you wait until the $http.get request is completed and then console.log(res.joke) is executed (as a normal asynchronous flow).

This is the plnkr:

http://embed.plnkr.co/XlNR7HpCaIhJxskMJfSg/

ES6 way (async - await)

(function(){
  async function getJoke(){
    let response = await fetch('http://api.icndb.com/jokes/random');
    let data = await response.json();
    return data.value;
  }

  getJoke().then((joke) => {
    console.log(joke);
  });
})();
Copy code

Undefined answered

2022-05-18

Link to answer

---

---

285

votes

Answer

Solution:

This is one of the places which two-way data binding or store concept that's used in many new JavaScript frameworks will work great for you...

So if you are using Angular, React, or any other frameworks which do two-way data binding or store concept, this issue is simply fixed for you, so in easy words, your result isundefined at the first stage, so you have gotresult = undefined before you receive the data, then as soon as you get the result, it will be updated and get assigned to the new value which response of your Ajax call...

But how you can do it in pure JavaScript or jQuery for example as you asked in this question?

You can use a callback, promise and recently observable to handle it for you. For example, in promises we have some function likesuccess() orthen() which will be executed when your data is ready for you. The same with callback or the subscribe function on an observable.

For example, in your case which you are using jQuery, you can do something like this:

$(document).ready(function(){
    function foo() {
        $.ajax({url: "api/data", success: function(data){
            fooDone(data); // After we have data, we pass it to fooDone
        }});
    };

    function fooDone(data) {
        console.log(data); // fooDone has the data and console.log it
    };

    foo(); // The call happens here
});
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For more information, study promises and observables which are newer ways to do this async stuff.

Undefined answered

2022-05-18

Link to answer

---

---

720

votes

Answer

Solution:

It's a very common issue we face while struggling with the 'mysteries' of JavaScript. Let me try demystifying this mystery today.

Let's start with a simple JavaScript function:

function foo(){
    // Do something
    return 'wohoo';
}

let bar = foo(); // 'bar' is 'wohoo' here
Copy code

That's a simple synchronous function call (where each line of code is 'finished with its job' before the next one in sequence), and the result is same as expected.

Now let's add a bit of twist, by introducing a little delay in our function, so that all lines of code are not 'finished' in sequence. Thus, it will emulate the asynchronous behavior of the function:

function foo(){
    setTimeout( ()=> {
        return 'wohoo';
   }, 1000)
}

let bar = foo() // 'bar' is undefined here
Copy code

So there you go; that delay just broke the functionality we expected! But what exactly happened? Well, it's actually pretty logical if you look at the code.

The functionfoo(), upon execution, returns nothing (thus returned value isundefined), but it does start a timer, which executes a function after 1 second to return 'wohoo'. But as you can see, the value that's assigned to bar is the immediately returned stuff from foo(), which is nothing, i.e., justundefined.

So, how do we tackle this issue?

Let's ask our function for a promise. Promise is really about what it means: it means that the function guarantees you to provide with any output it gets in future. So let's see it in action for our little problem above:

function foo(){
   return new Promise((resolve, reject) => { // I want foo() to PROMISE me something
    setTimeout ( function(){
      // Promise is RESOLVED, when the execution reaches this line of code
       resolve('wohoo') // After 1 second, RESOLVE the promise with value 'wohoo'
    }, 1000 )
  })
}

let bar;
foo().then( res => {
    bar = res;
    console.log(bar) // Will print 'wohoo'
});
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Thus, the summary is - to tackle the asynchronous functions like Ajax-based calls, etc., you can use a promise toresolve the value (which you intend to return). Thus, in short you resolve value instead of returning, in asynchronous functions.

UPDATE (Promises with async/await)

Apart from usingthen/catch to work with promises, there exists one more approach. The idea is to recognize an asynchronous function and then wait for the promises to resolve, before moving to the next line of code. It's still just thepromises under the hood, but with a different syntactical approach. To make things clearer, you can find a comparison below:

then/catch version:

function saveUsers(){
     getUsers()
      .then(users => {
         saveSomewhere(users);
      })
      .catch(err => {
          console.error(err);
       })
 }
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async/await version:

  async function saveUsers(){
     try{
        let users = await getUsers()
        saveSomewhere(users);
     }
     catch(err){
        console.error(err);
     }
  }
Copy code

Undefined answered

2022-05-18

Link to answer

---

---

804

votes

Answer

Solution:

Another approach to return a value from an asynchronous function, is to pass in an object that will store the result from the asynchronous function.

Here is an example of the same:

var async = require("async");

// This wires up result back to the caller
var result = {};
var asyncTasks = [];
asyncTasks.push(function(_callback){
    // some asynchronous operation
    $.ajax({
        url: '...',
        success: function(response) {
            result.response = response;
            _callback();
        }
    });
});

async.parallel(asyncTasks, function(){
    // result is available after performing asynchronous operation
    console.log(result)
    console.log('Done');
});
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I am using theresult object to store the value during the asynchronous operation. This allows the result be available even after the asynchronous job.

I use this approach a lot. I would be interested to know how well this approach works where wiring the result back through consecutive modules is involved.

Undefined answered

2022-05-18

Link to answer

---

---

599

votes

Answer

Solution:

While promises and callbacks work fine in many situations, it is a pain in the rear to express something like:

if (!name) {
  name = async1();
}
async2(name);
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You'd end up going throughasync1; check ifname is undefined or not and call the callback accordingly.

async1(name, callback) {
  if (name)
    callback(name)
  else {
    doSomething(callback)
  }
}

async1(name, async2)
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While it is okay in small examples it gets annoying when you have a lot of similar cases and error handling involved.

Fibers helps in solving the issue.

var Fiber = require('fibers')

function async1(container) {
  var current = Fiber.current
  var result
  doSomething(function(name) {
    result = name
    fiber.run()
  })
  Fiber.yield()
  return result
}

Fiber(function() {
  var name
  if (!name) {
    name = async1()
  }
  async2(name)
  // Make any number of async calls from here
}
Copy code

You can checkout the project here.

Undefined answered

2022-05-18

Link to answer

---

---

335

votes

Answer

Solution:

The following example I have written shows how to

• Handle asynchronous HTTP calls;
• Wait for response from each API call;
• Use Promise pattern;
• Use Promise.all pattern to join multiple HTTP calls;

This working example is self-contained. It will define a simple request object that uses the windowXMLHttpRequest object to make calls. It will define a simple function to wait for a bunch of promises to be completed.

Context. The example is querying the Spotify Web API endpoint in order to search forplaylist objects for a given set of query strings:

[
 "search?type=playlist&q=%22doom%20metal%22",
 "search?type=playlist&q=Adele"
]
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For each item, a new Promise will fire a block -ExecutionBlock, parse the result, schedule a new set of promises based on the result array, that is a list of Spotifyuser objects and execute the new HTTP call within theExecutionProfileBlock asynchronously.

You can then see a nested Promise structure, that lets you spawn multiple and completely asynchronous nested HTTP calls, and join the results from each subset of calls throughPromise.all.

NOTE Recent Spotifysearch APIs will require an access token to be specified in the request headers:

-H "Authorization: Bearer {your access token}" 
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So, you to run the following example you need to put your access token in the request headers:

var spotifyAccessToken = "YourSpotifyAccessToken";
var console = {
    log: function(s) {
        document.getElementById("console").innerHTML += s + "<br/>"
    }
}

// Simple XMLHttpRequest
// based on https://davidwalsh.name/xmlhttprequest
SimpleRequest = {
    call: function(what, response) {
        var request;
        if (window.XMLHttpRequest) { // Mozilla, Safari, ...
            request = new XMLHttpRequest();
        } else if (window.ActiveXObject) { // Internet Explorer
            try {
                request = new ActiveXObject('Msxml2.XMLHTTP');
            }
            catch (e) {
                try {
                  request = new ActiveXObject('Microsoft.XMLHTTP');
                } catch (e) {}
            }
        }

        // State changes
        request.onreadystatechange = function() {
            if (request.readyState === 4) { // Done
                if (request.status === 200) { // Complete
                    response(request.responseText)
                }
                else
                    response();
            }
        }
        request.open('GET', what, true);
        request.setRequestHeader("Authorization", "Bearer " + spotifyAccessToken);
        request.send(null);
    }
}

//PromiseAll
var promiseAll = function(items, block, done, fail) {
    var self = this;
    var promises = [],
                   index = 0;
    items.forEach(function(item) {
        promises.push(function(item, i) {
            return new Promise(function(resolve, reject) {
                if (block) {
                    block.apply(this, [item, index, resolve, reject]);
                }
            });
        }(item, ++index))
    });
    Promise.all(promises).then(function AcceptHandler(results) {
        if (done) done(results);
    }, function ErrorHandler(error) {
        if (fail) fail(error);
    });
}; //promiseAll

// LP: deferred execution block
var ExecutionBlock = function(item, index, resolve, reject) {
    var url = "https://api.spotify.com/v1/"
    url += item;
    console.log( url )
    SimpleRequest.call(url, function(result) {
        if (result) {

            var profileUrls = JSON.parse(result).playlists.items.map(function(item, index) {
                return item.owner.href;
            })
            resolve(profileUrls);
        }
        else {
            reject(new Error("call error"));
        }
    })
}

arr = [
    "search?type=playlist&q=%22doom%20metal%22",
    "search?type=playlist&q=Adele"
]

promiseAll(arr, function(item, index, resolve, reject) {
    console.log("Making request [" + index + "]")
    ExecutionBlock(item, index, resolve, reject);
}, function(results) { // Aggregated results

    console.log("All profiles received " + results.length);
    //console.log(JSON.stringify(results[0], null, 2));

    ///// promiseall again

    var ExecutionProfileBlock = function(item, index, resolve, reject) {
        SimpleRequest.call(item, function(result) {
            if (result) {
                var obj = JSON.parse(result);
                resolve({
                    name: obj.display_name,
                    followers: obj.followers.total,
                    url: obj.href
                });
            } //result
        })
    } //ExecutionProfileBlock

    promiseAll(results[0], function(item, index, resolve, reject) {
        //console.log("Making request [" + index + "] " + item)
        ExecutionProfileBlock(item, index, resolve, reject);
    }, function(results) { // aggregated results
        console.log("All response received " + results.length);
        console.log(JSON.stringify(results, null, 2));
    }

    , function(error) { // Error
        console.log(error);
    })

    /////

  },
  function(error) { // Error
      console.log(error);
  });Copy code

<div id="console" />Copy code

Undefined answered

2022-05-18

Link to answer

---

---

930

votes

Answer

Solution:

The short answer is, you have to implement a callback like this:

function callback(response) {
    // Here you can do what ever you want with the response object.
    console.log(response);
}

$.ajax({
    url: "...",
    success: callback
});
Copy code

Undefined answered

2022-05-18

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Solution:

JavaScript is single threaded.

The browser can be divided into three parts:

1. Event Loop

2. Web API

3. Event Queue

The event loop runs for forever, i.e., kind of an infinite loop. The event queue is where all your functions are pushed on some event (example: click).

This is one by one carried out of queue and put into the event loop which executes this function and prepares itself for the next one after the first one is executed. This means execution of one function doesn't start until the function before it in the queue is executed in the event loop.

Now let us think we pushed two functions in a queue. One is for getting a data from the server and another utilises that data. We pushed the serverRequest() function in the queue first and then the utiliseData() function. The serverRequest function goes in the event loop and makes a call to server as we never know how much time it will take to get data from server, so this process is expected to take time and so we busy our event loop thus hanging our page.

That's where Web API come into the role. It takes this function from the event loop and deals with the server making the event loop free, so that we can execute the next function from the queue.

The next function in the queue is utiliseData() which goes in the loop, but because of no data available, it goes to waste and execution of the next function continues until the end of the queue. (This is called Async calling, i.e., we can do something else until we get data.)

Let us suppose our serverRequest() function had a return statement in code. When we get back data from the server Web API, it will push it in the queue at the end of queue.

As it gets pushed at the end of the queue, we cannot utilise its data as there isn't any function left in o

Undefined answered

2022-05-18

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About the technologies asked in this question

PHP

PHP (from the English Hypertext Preprocessor - hypertext preprocessor) is a scripting programming language for developing web applications. Supported by most hosting providers, it is one of the most popular tools for creating dynamic websites. The PHP scripting language has gained wide popularity due to its processing speed, simplicity, cross-platform, functionality and distribution of source codes under its own license.
https://www.php.net/

JavaScript

JavaScript is a multi-paradigm language that supports event-driven, functional, and mandatory (including object-oriented and prototype-based) programming types. Originally JavaScript was only used on the client side. JavaScript is now still used as a server-side programming language. To summarize, we can say that JavaScript is the language of the Internet.
https://www.javascript.com/

React

React is currently the leader in JavaScript UI frameworks. First, the Facebook developers started working on this to make their job easier. An app called Facebook Ads grew very quickly, which meant complex management and support. As a result, the team began to create a structure that would help them with efficiency. They had an early prototype before 2011, and two years later, the framework was open source and available to the public. It is currently used by many business giants: AirBNB, PayPal, Netflix, etc.
https://reactjs.org/

Angular

Angular is one of the most powerful JavaScript frameworks out there. Google uses this platform to develop a Single Page Application (SPA). This development environment is known primarily because it provides developers with a better environment for combining JavaScript with HTML and CSS. More than half a million sites like google.com, youtube.com, etc. use Angular.
https://angular.io/

JQuery

JQuery is arguably the most popular JavaScript library with so many features for modern development. JQuery is a fast and concise JavaScript library created by John Resig in 2006. It is a cross-platform JavaScript library designed to simplify client-side HTML scripting. Over 19 million websites are currently using jQuery! Companies like WordPress, Facebook, Google, IBM and many more rely on jQuery to provide a kind of web browsing experience.
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https://backbonejs.org/

Node.js

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Ember.js

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CSS

CSS (Cascading Style Sheets) is a formal language for describing the appearance of a document written using a markup language. It is mainly used as a means of describing, decorating the appearance of web pages written using HTML and XHTML markup languages, but can also be applied to any XML documents, such as SVG or XUL.
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HTML

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https://www.w3.org/html/

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