title: Node.js check value in a few redis sets and return synchronously
body: <p>I have 7 sets and I need to check if value exists (<code>sismember</code>) at least in one set and return true or false.</p>
  
  <p>I need to get that value synchronously, like this:</p>
  
  <pre><code>const isExist = !!(_.max(_.range(7).map((day) =&gt; {
      redis.sismember(`blacklist${day}`, hashToken, function (err, res) {
         return res;
      });
  })));
  </code></pre>