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I am creating a Pacman game in JavaScript and have ran into a problem. I am trying to implement the ghost's movement. On each loop, I record the Tile Position of the ghosts var ghostX = Math.round(ghost.x / map.tileWidth); var ghostY = Math.round(ghost.y / map.tileHeight); There are four possible directions in which a ghost can move var moves = [ { 'direction': 'left', 'position': map.getTileLeft(0, ghostX, ghostY).x, 'distance': Math.sqrt(Math.pow((map.getTileLeft(0, ghostX, ghostY).x - pacmanX), 2) + Math.pow((map.getTileLeft(0, ghostX, ghostY).y - pacmanY), 2)), 'available': levelState.pathLeftAvailable(ghostX, ghostY) }, { 'direction': 'right', 'position': map.getTileRight(0, ghostX, ghostY).x, 'distance': Math.sqrt(Math.pow((map.getTileRight(0, ghostX, ghostY).x - pacmanX), 2) + Math.pow((map.getTileRight(0, ghostX, ghostY).y - pacmanY), 2)), 'available': levelState.pathRightAvailable(ghostX, ghostY) }, { 'direction': 'up', 'position': map.getTileAbove(0, ghostX, ghostY).y, 'distance': Math.sqrt(Math.pow((map.getTileAbove(0, ghostX, ghostY).x - pacmanX), 2) + Math.pow((map.getTileAbove(0, ghostX, ghostY).y - pacmanY), 2)), 'available': levelState.pathUpAvailable(ghostX, ghostY) }, { 'direction': 'down', 'position': map.getTileBelow(0, ghostX, ghostY).y, 'distance': Math.sqrt(Math.pow((map.getTileBelow(0, ghostX, ghostY).x - pacmanX), 2) + Math.pow((map.getTileBelow(0, ghostX, ghostY).y - pacmanY), 2)), 'available': levelState.pathDownAvailable(ghostX, ghostY) } ]; As you can see, I thought the best data structure for this would be an array of objects. Each move has several properties including the name of the direction, how far the move will place the ghost from Pacman, and whether it's a legal move. To find the closest tile, you use the distance formula. This is the square root of the squares of the sums of the x and y coordinates. I then created two variables to represent the closest and furthest tiles. This is where I received the error message var closestTile = moves.filter(m => m.available).sort((a,b) => a.distance - b.distance)[0].direction; var furthestTile = moves.filter( m => m.available).sort((a,b) => b.distance - a.distance)[0].direction; I need to find only legal moves, so it was necessary to filter() the array to find only those moves. The arrays then needed to be sorted by their distance. The first such element will be the result of the variable. But it couldn't find the direction property. The movement function is finished out like this var ghostVelocity = levelState.getGhostVelocity(); this.game.physics.arcade.collide(ghost, wallLayer, function() { var ghostDirection; if (ghost.direction == 'up' || ghost.direction == 'down') { ghost.y += ghost.direction == 'up' ? 1 : -1; if (ghost.vulnerable) { ghostDirection = furthestTile; } else { if (ghost == redGhost) { ghostDirection = closestTile; } else { ghostDirection = Math.random() > 0.5 ? 'left' : 'right'; } } ghost.body.velocity.y = 0; ghost.body.velocity.x = ghostDirection == 'left' ? -ghostVelocity : ghostVelocity; } else if (ghost.direction == 'left' || ghost.direction == 'right') { ghost.x += ghost.direction == 'left' ? 1 : -1; if (ghost.vulnerable) { ghostDirection = furthestTile; } else { if (ghost == redGhost) { ghostDirection = closestTile; } else { ghostDirection = Math.random() > 0.5 ? 'up': 'down'; } } ghost.body.velocity.x = 0; ghost.body.velocity.y = ghostDirection == 'up' ? -ghostVelocity : ghostVelocity; } ghost.direction = ghostDirection; }, null, this); As you can see, I am setting the ghost's direction property based on the closest tile to pacman. For reference, here are the four functions that determine whether a direction is available. There doesn't seem to be a problem here. pathRightAvailable: function(x, y) { return [x, x + 1, x + 2].every(function(xPosition) { return !map.hasTile(xPosition, y, 0); }); }, pathLeftAvailable: function(x, y) { return [x, x - 1, x - 2].every(function(xPosition) { return !map.hasTile(xPosition, y, 0); }); }, pathUpAvailable: function(x,y) { return [y, y - 1, y - 2].every(function(yPosition) { return !map.hasTile(x, yPosition, 0); }); }, pathDownAvailable: function(x,y) { return [y, y + 1, y + 2].every(function(yPosition) { return !map.hasTile(x, yPosition, 0); }); }, I've been working on this problem for some time but have ran into trouble. Any help is greatly appreciated