CHCH.js Roguelike with basic Line of Sight

rl2.html

<pre id="maze"></pre>
<script>
  'use strict'
  const maze = [
  '#########',
  '#@..#####',
  '###.#####',
  '#...#####',
  '#.#######',
  '#.#...###',
  '#......T#',
  '#########'
  ]

  let map = maze.map(line => line.split(''))
  let player = {x: 1, y: 1}

  function render (map) {
    let filteredMap = filterMapByLoS(map)
    document.getElementById('maze').innerHTML =
    filteredMap.map(characters => characters.join('')).join('<br>')
  }

  function getLine(x0, y0, x1, y1){
    var dx = Math.abs(x1-x0);
    var dy = Math.abs(y1-y0);
    var sx = (x0 < x1) ? 1 : -1;
    var sy = (y0 < y1) ? 1 : -1;
    var err = dx-dy;

    let points = []
    while(true){
      //points.push(x0, y0)
      points.push({x: x0, y: y0})

      if ((x0==x1) && (y0==y1)) break;
      var e2 = 2*err;
      if (e2 >-dy){ err -= dy; x0  += sx; }
      if (e2 < dx){ err += dx; y0  += sy; }
    }
    return points
  }

 function filterMapByLoS (m) {
 return  m.map((line, y)=>
       line.map((character, x) => {
         let obstructed = false
         for (let p of getLine(player.x, player.y, x, y)) {
           if (obstructed) {
             return ' '
             break;
           }
          if (map[p.y][p.x] === '#') obstructed = true
         }
         return character
       })
   )
 }


  render(map)

  const keyToDirection = {
    37: {x: -1, y: 0},
    38: {x: 0, y: -1},
    39: {x: 1, y: 0},
    40: {x: 0, y: 1}
  }

  document.onkeydown = function (e) {
    const direction = keyToDirection[e.keyCode]
    if (direction) {
      e.preventDefault()
      move(direction)
    }
  }

  const addPoints = (point1, point2) =>
  ({x: point1.x + point2.x, y: point1.y + point2.y})

  function move(direction) {
   const newPosition = addPoints(player, direction)
   const newCharacter = map[newPosition.y][newPosition.x]
   if (newCharacter === '.')
    teleportPlayer(newPosition)
   else if (newCharacter === 'T')
    alert("Congrats! You are a winner!")
 }

 function teleportPlayer ({x,y}) {
   map[player.y][player.x] = '.'
   map[y][x] = '@'
   player = {x, y}
   render(map)
 }
</script>