Display data json to table in react

I am assuming that you trying to call external file's method in current component. In your barang.js file export your function that holds json data like

export function tampildata() {
    return [{ "firstname": "first", "lastname": "f"}, {"firstname": "second", "lastname": "l"}];
}

or

export default {
  tampildata() {
    return [{ "firstname": "first", "lastname": "f"}, {"firstname": "second", "lastname": "l"}];
  }
};

Then in your keranjang.js file import your tampildata method and call that method in componentDidMount and set state like below

import React from 'react';
import ReactDOM from 'react-dom';
import { tampildata } from 'barang';

class TableComponent extends React.Component {
    constructor(props) {
        super(props)
        this.state = {
            json: []
        }
    }

    componentDidMount() {
        this.setState((prevState) => {
            return {
                json: tampildata()
            }
        })
    }

    render() {
        return (
            <div>
                <table>
                    <thead>
                        <th>First Name</th>
                        <th>Last Name</th>
                    </thead>
                    <tbody>
                        {this.state.json.map((data, i) => {
                            return (
                                <tr key={i}>
                                    <td>{data.firstname}</td>
                                    <td>{data.lastname}</td>
                                </tr>
                            )
                        })}
                    </tbody>
                </table>
            </div>
        )
    }
}


ReactDOM.render(
  <TableComponent />, 
  document.getElementById("app")
);

Here is the working jsfiddle. Hope this will helps you!