title: how to validate files before uploading in angular 6
body: <p>How can I <code>validate</code> files before uploading in angular 4 and above?<br>
  i want <code>file type</code> and <code>file size</code> validation in angular 4 and above.<br>
  <a href="https://i.stack.imgur.com/rPIC3.png" rel="noreferrer">Screenshot of my issue</a></p>
  
  <p>for each and every file I am getting correct file size and type except <strong>.msg</strong> file. How to get 
  file type as <strong>application/vnd.ms-outlook
  application/octet-stream</strong>
   for <strong>outlook</strong> files. Please help me out.</p>