title: Regex expression for empty string that accept number with 1 place decimal?
body: <p>I want a regular expression for empty string that accept number with 1
   place decimal</p>
  
  <p>Accepted value</p>
  
  <pre><code>[blank space]
  1.1
  2.1
  3.1
  22
  12
  0
  empty string
  </code></pre>
  
  <p>Not accepted</p>
  
  <pre><code>q.q
  1q
  .0
  .00
  </code></pre>
  
  <p>Tried</p>
  
  <pre><code>^[0-9]+(\.[0-9]{1,1})?$
  </code></pre>
  
  <p><strong>but it's no idea for blank space</strong></p>