Learning Javascript: What is AJAX? and How to use it?

What is AJAX?

AJAX stands for A synchronous J JavaScript A and X ML.

AJAX serves to:

Retrieve data from the server in the background ;
Update web views without having to reload the browser;
Send data to the server in the background .

Basically AJAX only uses objects XMLHttpRequest to communicate with the server.

We can see the AJAX process through inspecting elements in a web browser , then open the Network tab and activate the XHR (XML HTTP Request) filter .

Oh yeah, even though AJAX has the word "XML" ... Not that it only supports XML format .

AJAX also supports JSON , Plain Text and HTML formats .

How to use Ajax in JavaScript

The steps to using AJAX like this:

Create Ajax Objects
```
var xhr = new XMLHttpRequest();
```

Determine the Function of the Handler for Events

xhr.onreadystatechange = function() { ... };
xhr.onload = function() { ... };
xhr.onerror = function() { ... };
xhr.onprogress = function() { ... };

Determine the Method and URL
```
xhr.open("GET", url, true);
```
Send Request
```
xhr.send();
```

Okay…

Let's try it.

Make an HTML file with the contents as follows:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Belajar Dasar Ajax</title>
</head>
<body>
    <h1>Tutorial Ajax</h1>
    <div id="hasil"></div>
    <button onclick="loadContent()">Load Content</button>

    <script>
        function loadContent(){
            var xhr = new XMLHttpRequest();
            var url = "https://api.github.com/users/petanikode";
            xhr.onreadystatechange = function(){
                if(this.readyState == 4 && this.status == 200){
                    document.getElementById("hasil").innerHTML = this.responseText;
                }
            };
            xhr.open("GET", url, true);
            xhr.send();
        }
    </script>
</body>
</html>

The result:

In the example above, we retrieve data from the Github server using the GET method. Then the results are directly entered into the element <div id="hasil">.

The event we use is onreadystatechange, in this event we can check the AJAX state and status.

if(this.readyState == 4 && this.status == 200){
    //...
}

Code state 4means done and status 200means success. Here is a list of AJAX state codes. 1

Code	State	Information
0	UNSENT	An AAJAX object has been created but has not called the method `open()`.
1	OPENED	The method `open()`has been called.
2	HEADERS_RECEIVED	The method `send()`has been called, and here is a status header.
3	LOADING	Downloading; is downloading data.
4	DONE	AJAX operation is complete.

While for the status header 200is the status of HTTP Request. Usually the above code 200means good and below 200means bad.

Then try to pay attention to this code:

xhr.open("GET", url, true);

There are three parameters that we give to the method open():

GET is the request method to be used;
url is the destination URL address;
trueis to execute AJAX asynchronously .

Let's continue with the other example. Please change the contents of the HTML file that was like this:

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Belajar Dasar Ajax</title>
</head>

<body>
    <h1>Tutorial Ajax <button id="btn-clear" onclick="clearResult()">Clear</button></h1>
    <div id="hasil"></div>
    <button id="button" onclick="loadContent()">Load Content</button>

    <script>
        function loadContent() {
            var xhr = new XMLHttpRequest();
            var url = "https://api.github.com/users/petanikode";

            xhr.onloadstart = function () {
                document.getElementById("button").innerHTML = "Loading...";
            }

            xhr.onerror = function () {
                alert("Gagal mengambil data");
            };

            xhr.onloadend = function () {
                if (this.responseText !== "") {
                    var data = JSON.parse(this.responseText);
                    var img = document.createElement("img");
                    img.src = data.avatar_url;
                    var name = document.createElement("h3");
                    name.innerHTML = data.name;

                    document.getElementById("hasil").append(img, name);
                    document.getElementById("button").innerHTML = "Done";

                    setTimeout(function () {
                        document.getElementById("button").innerHTML = "Load Lagi";
                    }, 3000);
                }
            };

            xhr.open("GET", url, true);
            xhr.send();
        }

        function clearResult() {
            document.getElementById("hasil").innerHTML = "";
        }
    </script>
</body>
</html>

The result:

Sending Data to Server with AJAX

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Belajar Dasar Ajax</title>
</head>

<body>
    <h1>Kirim Data dengan Ajax</h1>
    <form method="POST" onsubmit="return sendData()">
        <p>
            <label>Title</label>
            <input type="text" id="title" placeholder="judul artikel">
        </p>
        <p>
            <label>Isi Artikel</label><br>
            <textarea id="body" placeholder="isi artikel..." cols="50" rows="10"></textarea>
        </p>
        <input type="submit" value="Kirim" />
    </form>

    <script>
        function sendData() {
            var xhr = new XMLHttpRequest();
            var url = "https://jsonplaceholder.typicode.com/posts";

            var data = JSON.stringify({
                title: document.getElementById("title").value,
                body: document.getElementById("body").value,
                userId: 1
            });

            xhr.open("POST", url, true);
            xhr.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
            xhr.onload = function () {               
                console.log (this.responseText);
            };

            xhr.send(data);
            return false;
        }
    </script>
</body>
</html>

The result:

The data transmission is only for simulation. Data will not actually be sent to the server https://jsonplaceholder.typicode.com/posts .

AJAX Using JQuery

JQuery is a Javascript library that simplifies Javascript functions. In JQuery, AJAX can be created like this:

// load data ke elemen tertentu via AJAX
$(selector).load(URL,data,callback);

// ambil data dari server
$.get(URL,callback);

// kirim data dari Server
$.post(URL,data,callback);

Let's try ...

Create a new file named ajax-jquery.htmlthen fill in the following code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Belajar AJAX dengan JQuery</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>
</head>
<body>
    <h1>Load Data</h1>
    <pre id="result"></pre>
    
    <script>
        $("#result").load("https://api.github.com/users/petanikode");
    </script>
</body>
</html>

The result:

With the function $("#result").load(), we can retrieve data with AJAX and directly display it on the selected element.

The JQuery function is load()suitable for taking parts of HTML to display.

Another example uses the GET method:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Belajar AJAX dengan JQuery</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>
</head>
<body>
    <h1>Load Data</h1>
    <img id="avatar" src="" width="100" height="100">
    <br>
    <h3 id="name"></h3>
    <p id="location"></p>
    
    
    <script>
        var url = "https://api.github.com/users/petanikode";
        $.get(url, function(data, status){
            $("#avatar").attr("src", data.avatar_url);
            $("#name").text(data.name);
            $("#location").text(data.location);
        });
    </script>
</body>
</html>

The result:

Now to send data with AJAX in JQuery, the way is almost the same as taking data with $.get().

<script>
var url = "https://jsonplaceholder.typicode.com/posts";
var data = {
    title: "Tutorial AJAX dengan JQuery",
    body: "Ini adalah tutorial tentang AJAX",
    userId: 1
};
$.post(url, data, function(data, status){
    // data terkkirim, lakukan sesuatu di sini
});
</script>

AJAX uses the Fetch API

Fetch means to take. The fetch method can be an alternative to AJAX.

This method starts to appear in the ES6 version of JavaScript.

The difference between XMLHttpRequestand JQuery is:

Fetch will return a promise;
By default (default), fetch will not send or receive cookies from the server. 2
Fetch can be used in web browsers as well as Nodejs with modules node-fetch.

The following is the basic syntax of using Fetch .

fetch('http://example.com/movies.json')
  .then(function(response) {
    return response.json();
  })
  .then(function(myJson) {
    console.log(JSON.stringify(myJson));
  });

And for sending data using the POST method, it looks like this:

fetch(url, {
        method: "POST", // *GET, POST, PUT, DELETE, etc.
        mode: "cors", // no-cors, cors, *same-origin
        cache: "no-cache", // *default, no-cache, reload, force-cache, only-if-cached
        credentials: "same-origin", // include, *same-origin, omit
        headers: {
            "Content-Type": "application/json",
            // "Content-Type": "application/x-www-form-urlencoded",
        },
        redirect: "follow", // manual, *follow, error
        referrer: "no-referrer", // no-referrer, *client
        body: JSON.stringify(data), // body data type must match "Content-Type" header
    })
    .then(response => response.json()); // parses JSON response into native Javascript objects

Let's try ...

The following is an example of taking data using fetch :

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Belajar Dasar Ajax dengan Fetch</title>
</head>
<body>
    <h1>Tutorial Ajax dengan Fetch</h1>
    <button onclick="loadContent()">Load Content</button>
    <div id="hasil"></div>

    <script>
        function loadContent(){
            var url = "https://jsonplaceholder.typicode.com/posts/";
            fetch(url).then(response => response.json())
                .then(function(data){
                    var template = data.map(post => {
                        return `
                        <h3>${post.title}</h3>
                        <p>${post.body}</p>
                        <hr>
                        `;
                    });

                    document.getElementById("hasil").innerHTML = template.join('<br>');
                }).catch(function(e){
                    alert("gagal mengambil data");
                });
        }
    </script>
</body>
</html>

The result:

Ajax Using Axios

Axios is almost the same as fetch . The difference is Axios is a library while fetch is an API available in web browsers.

Axios can also be used in both web browsers and Nodejs.

An AJAX example with Axios:

axios.get('https://jsonplaceholder.typicode.com/posts/')
  .then(function (response) {
    // handle success
    console.log(response);
  })
  .catch(function (error) {
    // handle error
    console.log(error);
  })
  .then(function () {
    // always executed
  });

Let's try it in HTML:

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Tutorial AJAX dengan AXIOS</title>
    <script src="https://unpkg.com/axios/dist/axios.min.js"></script>
</head>

<body>
    <h1>Tutorial AJAX dengan AXIOS</h1>
    <button id="btn-load" onclick="loadContent()">Load Content</button>
    <div id="result"></div>

    <script>
        function loadContent() {
            document.getElementById("btn-load").innerHTML = "loading...";
            document.getElementById("btn-load").setAttribute("disabled", "true");
            axios.get('https://jsonplaceholder.typicode.com/posts/')
                .then(function (response) {
                    var template = response.data.map(post => {
                        return `
                        <h3>${post.title}</h3>
                        <p>${post.body}</p>
                        <hr>
                        `
                    }).join("");

                    document.getElementById("result").innerHTML = template;
                })
                .catch(function (error) {
                    // handle error
                    console.log(error);
                })
                .then(function () {
                    document.getElementById("btn-load").innerHTML = "Done";
                    document.getElementById("btn-load").removeAttribute("disabled");
                });
        }
    </script>
</body>

</html>

The result:

Reference: https://www.petanikode.com/javascript-ajax/

Category

Learning Javascript: What is AJAX? and How to use it?

What is AJAX?

How to use Ajax in JavaScript

Sending Data to Server with AJAX

AJAX Using JQuery

AJAX uses the Fetch API

Ajax Using Axios

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