title: Why we are using _ in this expression str.replace(/[\W_]/g, '').toLowerCase(); We could have used /[\W]/g also but why are we using underscore?
body: <p>It is a javascript question.I was solving palindromes question on freecodecamp.Let me write the full code here:</p>
  
  <pre><code> function palindrome(str) {
   var normalizedStr = str.replace(/[\W_]/g, '').toLowerCase();
   var reverseStr = normalizedStr.split('').reverse().join('');
    return normalizedStr === reverseStr;
   }
  </code></pre>