title: What does the JSLint error 'body of a for in should be wrapped in an if statement' mean?
body: <p>I used <a href="http://www.jslint.com/" rel="noreferrer">JSLint</a> on a JavaScript file of mine. It threw the error:</p>
  
  <pre><code>for( ind in evtListeners ) {
  </code></pre>
  
  <blockquote>
    <p>Problem at line 41 character 9: The body of a for in should be
    wrapped in an if statement to filter unwanted 
    properties from the prototype.</p>
  </blockquote>
  
  <p>What does this mean?</p>