title: How to validate textbox while user are typing values Using javascript
body: <p>I have some troubles to validate user input while they are typing.</p>
  
  <p>For example: the valid range is 600-800 and user is trying to type 700</p>
  
  <pre><code>When textbox is empty: show nothing
  
  When textbox is 7: show red
  
  When textbox is 70: show red
  
  When textbox is 700:show nothing
  </code></pre>
  
  <p>I hope I can do it in js, can anyone help me?</p>