title: Unexpected output from in JavaScript operator
body: <p>I have a function as defined below:</p>
  
  <pre><code>function makeUser(name, age) {
    return {
      name,
      age
      // ...другие свойства
    };
  }
  </code></pre>
  
  <p>I then create a user variable and atempt to console.log() using the <code>in</code> operator</p>
  
  <pre><code>let user = makeUser('John', 30);
  
  console.log('name' in makeUser); // true - why is true??
  console.log('age' in makeUser); // false - why is false??
  </code></pre>
  
  <p>The first log() evaluates to true, while the second evaluates to false.
  I would expect them both to be true. </p>
  
  <p>Why is this?</p>