How to post a file from a form with Axios

Question

Using raw HTML when I post a file to a flask server using the following I can access files from the flask request global:

<form id="uploadForm" action='upload_file' role="form" method="post" enctype=multipart/form-data>
    <input type="file" id="file" name="file">
    <input type=submit value=Upload>
</form>

In flask:

def post(self):
    if 'file' in request.files:
        # ....

When I try to do the same with Axios the flask request global is empty:

<form id="uploadForm" enctype="multipart/form-data" v-on:change="uploadFile">
    <input type="file" id="file" name="file">
</form>

<script>
function uploadFile(event) {
    const file = event.target.files[0]
    axios.post('upload_file', file, {
        headers: {
          'Content-Type': 'multipart/form-data'
        }
    })
}
</script>

If I use the same uploadFile function above but remove the headers json from the axios.post method I get in the form key of my flask request object a csv list of string values (file is a .csv).

How can I get a file object sent via axios?

Answer 1

Add the file to a formData object, and set the Content-Type header to multipart/form-data.

var formData = new FormData();
var imagefile = document.querySelector('#file');
formData.append("image", imagefile.files[0]);
axios.post('upload_file', formData, {
    headers: {
      'Content-Type': 'multipart/form-data'
    }
})