how to open (doc, ppt, xlsx, pdf, jpg ,png) file using ionic native file opener

finally i got solution.

let fileExtn=file_name.split('.').reverse()[0];
let fileMIMEType=this.getMIMEtype(fileExtn);
         this.fileOpener.open("file:///storage/emulated/0/download/"+ file_name+"", fileMIMEType)
                .then(() => console.log('File is opened'))
                .catch(e => console.log('Error openening file', e));

make other function for MIMEtype

getMIMEtype(extn){
  let ext=extn.toLowerCase();
  let MIMETypes={
    'txt' :'text/plain',
    'docx':'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
    'doc' : 'application/msword',
    'pdf' : 'application/pdf',
    'jpg' : 'image/jpeg',
    'bmp' : 'image/bmp',
    'png' : 'image/png',
    'xls' : 'application/vnd.ms-excel',
    'xlsx': 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
    'rtf' : 'application/rtf',
    'ppt' : 'application/vnd.ms-powerpoint',
    'pptx': 'application/vnd.openxmlformats-officedocument.presentationml.presentation'
  }
  return MIMETypes[ext];
}