how use formdata on vuejs3

Question

(front vuejs3 + axios | back nodejs + prisma sql)

I have a function to create a post. When I use it with postman it works.

But when I use it with frontend it returns me a formdata = null

On this.selectedFile, i have the file. But i have this error :

C:\Users\gbl\Documents\backend\controllers\post.js:38 attachment: ${req.protocol}://${req.get('host')}/images/${req.file.filename}, ^ TypeError: Cannot read properties of undefined (reading 'filename')

can you help me please ?

data () {
    return {
        title: '',
        content: '',
        userId: '',
        selectdFile: null,
    }
},
methods: {
    onFileSelected (event) {
        this.selectedFile = event.target.files[0];
        console.log(this.selectedFile);
    },
    async createPost() {
        const formData = new FormData();
        formData.append( 'image', this.selectedFile, this.selectedFile.name );

        console.log('ok')
        console.log(formData);
        const id = localStorage.getItem('userId');
        const response = await axios.post('http://localhost:3000/api/post', {
            title: this.title,
            content: this.content,
            userId: parseInt(id),
            attachment: this.selectedFile,

        }, {
            headers: {
                Authorization: 'Bearer ' + localStorage.getItem('token')
            },
        });
        console.log(response);
    },

Voici le resultat :