appach.js

 methods: {
    uploadImage(event) {
      let img = new FormData();
      img.append("avatar", event.target.files[0]);
      const base = {
        baseURL: this.$store.state.endpoints.baseUrl,
        headers: {
          // JWT token !!!
          Authorization: `JWT ${this.$store.state.jwt}`,
          "Content-Type": "multipart/form-data"
        },
        xhrFields: {
          withCredentials: true
        }
      };
      const axiosInstance = axios.create(base);
      axiosInstance({
        url: "http://127.0.0.1:8000/userDetails/",
        data: img,
        method: "patch"
      })
        .then(response => {
          console.log(response);
          this.snackbar = true
        })
        .catch(error => {
          console.log(error);
          console.debug(error);
          console.dir(error);
        });
    },
    onButtonClick() {
      this.$refs.uploader.click();
    }
  },