title: Use underscore to change one property of objects in an array
body: <p>I'm hoping to take advantage of underscore to avoid writing <code>for</code> loops throughout my code base. I'm using <code>map</code> in place of a <code>for</code> loop like so:</p>
  
  <pre><code>body.tags = _.map(body.tags, function(tag) {
    return {
      id: tag.id,
      userId: tag.userId,
      createDate: tag.createDate,
      tag: tag.tag.toLowerCase(),
    };
  });
  </code></pre>
  
  <p>My question is, is there a way to do this without specifying the properties that won't be changing (everything but <code>tag</code>)? It seems like overkill to specify fields like <code>id: tag.id</code>.</p>