Post with Angular multipart data

snippet.js

postFile(uri: string, data: any, file: any = null): Observable<any>{

    if(file) {
      let t = data;
      let formData: FormData = new FormData();
      console.log(file);
      formData.append('file', file.originFileObj, file.name);
      Object.keys(data).forEach((key)=>{formData.append(key,data[key])});
      data = formData;
    }


    return this.rest.post(uri, data, {headers: this.headers, withCredentials: true});
}