game.js

const readline = require('readline');

readline.emitKeypressEvents(process.stdin);
process.stdin.setRawMode(true);

process.stdin.on('keypress', (str, key) => {
  if (key.ctrl && key.name === 'c') {
    process.exit();
  }
  handleKey(key);
});

const player = { x: 0, y: 0};
const board = ('-'.repeat(100) + '\n')
  .repeat(20)
  .split('\n')
  .map(line => line.split(''));

function handleKey(key) {
  const movePlayer = ({
    up: () => player.y--,
    down: () => player.y++,
    left: () => player.x--,
    right: () => player.x++,
  })[key.name];

  if (movePlayer) {
    movePlayer();
  }
  render();
  console.log(key);
}

function render() {
  const screen = board
    .map((line, lineIndex) => {
      return line
        .map((dash, dashIndex) => {
          return dashIndex === player.x && lineIndex === player.y ? 'O' : dash;
         })
        .join('');
    })
    .join('\n');

  console.clear();
  console.log(screen);
}
render();