How can JavaScript upload a blob ?

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There are many ways to upload a blob (a group of bytes that holds the data stored in a file) in JavaScript, using XMLHttpRequest, Fetch API, jQuery. In this tutorial, we will discuss the two most common ways that are supported by a majority of the browsers.

Note: To test our HTTP request, you can use minimal express server. You can also use any online testing tool like webhook.site.

Fetch API: The Fetch API allows web browsers to send and receive data from the servers through HTTP requests. It is an easy-to-use version of XMLHttpRequest. The fetch() method returns a Promise which then can be chained with then() and catch() for better error handling. It is supported by all the modern browsers except IE.

Syntax:

fetch( url,  // API endpoint
{
    method:"",  // HTTP Method (GET, POST, PUT, DELETE)
    body: {},   // Data to be sent
}).then(response => {

    // handle the response
})
.catch(e => {

    // handle the error
});

Example:

JavaScript

<script> 
    function uploadBlob() { 
        const blob = 
            new Blob( 
                ["This is some important text"], 
                { type: "text/plain" } 
            ); 
  
        // Creating a new blob   
        // Hostname and port of the local server 
        fetch('http://localhost:3000', { 
  
            // HTTP request type 
            method: "POST", 
  
            // Sending our blob with our request 
            body: blob 
        }) 
        .then(response => alert('Blob Uploaded')) 
        .catch(err => alert(err)); 
    } 
  
    document.addEventListener('load', uploadBlob()) 
</script> 

Output:

AJAX: It is a set of web applications that can send and retrieve data from a server asynchronously without reloading the current page. Please import or load jQuery before calling the ajax function.

Syntax:

$.ajax({
    url: "",       // API Endpoint
    type: "",      // HTTP Method (GET, POST, PUT, DELETE)
    data: {},      // Data to be sent
    
    // Specifies how the form-data should be encoded
    enctype: 'multipart/form-data',
    success: function(data) {
    
    // Handle the response
}, error: function(e) {

    // Handle the error
}
});

Example:

HTML

<!DOCTYPE html> 
<html lang="en"> 
  
<head> 
    <script src= 
"https://code.jquery.com/jquery-3.6.0.min.js"> 
    </script> 
</head> 
  
<body> 
    <script> 
        function uploadBlob() { 
            const blob = new Blob( 
                ["This is some important text"], 
                { type: "text/plain" } 
            ); 
  
            // Creating a new blob   
            $.ajax({ 
  
                // Hostname and port of the local server 
                url: "http://localhost:3000/", 
  
                // HTTP request type 
                type: "POST", 
  
                // Sending blob with our request 
                data: blob, 
                processData: false, 
                contentType: false, 
                success: function (data) { 
                    alert('Blob Uploaded') 
                }, 
                error: function (e) { 
                    alert(e); 
                } 
            }); 
  
        } 
        $(document).on('load', uploadBlob()); 
    </script> 
</body> 
  
</html> 