title: regex to find numbers with unique digits
body: <p>I want to find 10 digit numbers with no repeat digits, for example:</p>
  
  <pre><code>1123456789 //fail, there are two 1's
  6758951230 //fail, there are two 5's
  6789012345 //pass, each digit occurs once only. 
  </code></pre>
  
  <p>at the moment I am using regex but can only match 10digits numbers(it doesnt check for duplicates. I am using this regex:</p>
  
  <pre><code>[0-9]{10}
  </code></pre>
  
  <p>Can this be done with regex or is there a better way to achieve this?</p>