How to create an instance of an imported class in another class
<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>