How To Add Header Data In Xmlhttprequest When Using Formdata

When working with XMLHttpRequest and FormData in JavaScript, adding header data is a common requirement. This task is essential for sending additional information along with your requests, whether it be authentication tokens, content types, or other metadata. In this article, I'll walk you through the process of adding header data in XMLHttpRequest when using FormData.

To set header data in your XMLHttpRequest object, you first need to create a new instance of the object. This can be done using the following code snippet:

var xhr = new XMLHttpRequest();

Next, you'll need to specify the type of request you want to make, such as `GET`, `POST`, `PUT`, or `DELETE`. For example, if you're sending form data using the `POST` method:

xhr.open('POST', 'your_url_here', true);

After setting up the request type and URL, you can add your custom headers to the `XMLHttpRequest` object. To add header data when using `FormData`, you can set the necessary headers using the `setRequestHeader` method. Here's an example of how you can add a custom header named `X-Auth-Token` with a corresponding token value:

xhr.setRequestHeader('X-Auth-Token', 'your_token_here');

Additionally, if you need to specify the content type of the data you're sending, you can set the appropriate `Content-Type` header. When sending FormData, the content type is automatically set to `multipart/form-data`, so you may not need to set it explicitly unless required by your server.

To send formData along with your request, you can simply pass the `FormData` object as the parameter to the `send` method of the `XMLHttpRequest` object. For example:

var formData = new FormData();
formData.append('file', fileInput.files[0]);

xhr.send(formData);

This code snippet sends a file uploaded via a file input element along with any additional header data you've set.

It's important to note that when adding custom headers, you should ensure that they adhere to the CORS (Cross-Origin Resource Sharing) policy of the server you are sending the request to. Failure to comply with CORS policies may result in the browser blocking the request for security reasons.

In conclusion, adding header data in XMLHttpRequest when using FormData is a relatively straightforward process that involves creating an XMLHttpRequest object, setting the necessary headers, and sending the FormData object along with the request. By following the steps outlined in this article, you'll be able to customize your requests with additional header data to meet your application's requirements.