Live Demo: JavaScript Set Header in Ajax POST Request

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>JavaScript Set Header in Ajax POST Request</title>
<script>
function addSubscriber() {
    // Creating the XMLHttpRequest object
    var request = new XMLHttpRequest();

// Instantiating the request object
    request.open("POST", "/examples/php/add-subscriber.php");
    
    // Specifying the MIME type of the request body
    request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

// Defining event listener for readystatechange event
    request.onreadystatechange = function() {
        // Check if the request is compete and was successful
        if(this.readyState === 4 && this.status === 200) {
            // Inserting the response from server into an HTML element
            document.getElementById("result").innerHTML = this.responseText;
        }
    };

// Retrieving the form data
    var email = document.getElementById("email").value;
    console.log(email);

// Sending the request to the server
    request.send("email=" + email);
}
</script>
</head>
<body>
    <form id="myForm">
        <h2>Subscribe to our newsletter</h2>
        <p>Enter a dummy email address to see how it works.</p>
        <label>Email:</label>
        <div><input type="text" id="email"></div>
        <p><button type="button" onclick="addSubscriber()">Subscribe</button></p>
    </form>
    <div id="result">
        <p>Content of the result DIV box will be replaced by the server response</p>
    </div>
</body>
</html>