title: What is global.Promise in express
body: <p>I am learning express and mongo and I came across a line <code>mongoose.Promise = global.Promise</code> which I don't understand where the <code>global.Promise</code> came from?</p>
  <p>Following is the code</p>
  <pre><code>import express from &quot;express&quot;;
  import routes from &quot;./src/routes/crmRoutes&quot;;
  import mongoose from &quot;mongoose&quot;
  let app = express();
  let PORT = 9666;
  
  routes(app)
  
  app.get(&quot;/&quot;, (req, res)=&gt;{
      res.send(&quot;hello from node and express&quot;)
      console.log(global.Promise)
  })
  </code></pre>