state = {
    users: [
      { id: 1, name: 'Chris', age: 20 },
      { id: 2, name: 'Max', age: 1 },
      { id: 3, name: 'Jean', age: 23 },
      { id: 4, name: 'Luc', age: 30 }
    ]
  }

  userList = this.state.users.map(user => {
    return (
    <div key={user.id} className="column">
      <UserCard name={user.name} age={user.age} onClick={this.userClickHandler} />
    </div>);
  });

  userClickHandler = () => {
    console.log('clicked !');
  };

  render() {
    return (
    <div className="columns">
      {this.userList}
    </div>);
  }

<div className="columns">
  { this.state.users.map(user => {
    return (
    <div key={user.id} className="column" onClick={this.userClickHandler}>
      <UserCard name={user.name} age={user.age} />
    </div>);
  }) }
</div>);