my fix

gistfile1.txt

import React, { useEffect, useState } from 'react';

function Card({ title, text, target, linkTitle, href, rel, onClick }) {
  return (
    <div className="card">

        <div className="card__title">{title}</div>

        <div className="card__text">{text}</div>
        <a className={`default-link card__link`} target={target} rel={rel} href={href} onClick={onClick}>
          {linkTitle}
        </a>
    </div>
  );
}

export default function Page () {
  const [cards, setCards] = useState();

  useEffect(async () => {
    var data = await fetch('https://my-json-server.typicode.com/savayer/demo/posts');
    let json = data.json();

    let newData;
    json.forEach((item) => {
      newData.id = item.id;
      newData.title = item.title;
      newData.link_title = item.link_title;
      newData.link = item.link;
      newData.text = item.body.en.substr(0, 50) + '...';
    });

    setCards(newData);
  });

  function analyticsTrackClick(url) {
    // sending clicked link url to analytics
    console.log(url);
  }

  return (
    <div>
    {cards.map(function (item) {
      return (
        <Card title={item.title.en} linkTitle={item.link_title} href={item.link} text={item.text} onClick={analyticsTrackClick} />
      );
    })}
    </div>
  );
}