I have started learning React and have below component:

```
import React, { Component } from 'react';
class Test extends Component{
    handler(){
        console.log(this);
        return function(){
            console.log(this);
        }
    }
    render(){
       {this.handler()()}
       return null;
    }
}
export default Test;

```

When this component is mounted in browser, the console prints that`this` inside the function returned by handler is undefined.

I don't understand why it is undefined if the component has already mounted. Can you people help me to find the reason for this and a possible correction.

thank You!