I am validating file extensions before uploading.

We are using File reader to read contents. But while accepting .zip file is there a way to get the file extensions inside the zip file which we are trying to upload.

const validFileExtensions:string[]=['doc','xls','html','zip'];

private ValidateFileExtesnion(file:File)
{
   if(this.validFileExtensions.forEach(ext=>{
         result.push(file.name.endsWith(ext)?true:false,);
    });

    if(result.indexOf(true)==-1)
    {
      alert("Not valid File");
    }

}

Please let me know how can we validate file extensions inside the zip file with out using any using any plugins .