Axios upload multiple files

file.vue

<input type="file" ref="file" multiple="multiple">

submitFiles() {

    let formData = new FormData();

    for( var i = 0; i < this.$refs.file.files.length; i++ ){
        let file = this.$refs.file.files[i];
        console.log(file);
        formData.append('files[' + i + ']', file);
    }

    axios.post( '/fileupload', formData, {
        headers: {
            'Content-Type': 'multipart/form-data'
        },
      }
    ).then(function(){
    })
    .catch(function(){
    });
}