title: Regular expression to allow spaces between words
body: <p>I want a regular expression that prevents symbols and only allows letters and numbers. The regex below works great, but it doesn't allow for spaces between words.</p>
  
  <pre><code>^[a-zA-Z0-9_]*$
  </code></pre>
  
  <p>For example, when using this regular expression "HelloWorld" is fine, but "Hello World" does not match.</p>
  
  <p>How can I tweak it to allow spaces?</p>