Reward.js

const Rewards = {

  rewardList: [
    {
      id: 1,
      title: "dvssvzev",
      selected: false,
    },
    {
      id: 2,
      title: "dvssvzev",
      selected: false,
    },
    {
      id: 3,
      title: "dvssvzev",
      selected: false,
    }
  ],

  selectReward(id) {
    this.rewardList.find((reward) => reward.id === id).selected = true;
  }
}

export default Rewards;

Merci :)