title: JS regex which allows lowercase letters and underscore (in between )
body: <p>I need to create a JS regext which only allow small letter and underscore (not in first or last ) .</p>
  
  <blockquote>
    <p>eg . abc_xyz or abcc or abc____xyc___sss</p>
  </blockquote>
  
  <p>I am trying something like </p>
  
  <pre><code>/^[a-z]+$/
  </code></pre>
  
  <p>but not understand how to manage underscore </p>