title: How to create an instance of an imported class in another class
body: <p><strong>User.js</strong></p>
  
  <pre><code>class User {
  
    constructor() {
      this.fisrtName
      this.lastName
    }
  
    get fullName() {
      `${this.firtName} ${this.lastName}`
    }
  
  }
  
  export default User
  </code></pre>
  
  <p><strong>Test.js</strong></p>
  
  <pre><code>import React from 'react'
  import {User} from './User'
  
  class Test extends React.Component {
  
    testClick(e) {
      const user = new User() //error! because User is undefined.
    }
  
    render() {
      return (
        &lt;button onClick={this.testClick.bind(this)}&gt;test&lt;/button&gt;
      )
    }
  
  }
  
  export default Test
  </code></pre>