title: When does the web3 object get injected into a webpage?
body: <p>I have a node.js app which was generated by the express generator. I want to use the web3 object injected by the Metamask plugin, but when I try to console.log(process.web3), it is undefined. When I type window.web3 into the browser's developer console, it returns the web3 object.</p>
  
  <p>Does anybody know when the web3 object is injected and where in an express app I can assign something like</p>
  
  <pre><code>var web3 = process.web3;
  </code></pre>