Unlimited Conway's Life | Codewars

unlimited_life.js

let ArrayUtils = {}

ArrayUtils.getSquare = function(x, y) {
  return Array.apply(null, Array(y)).map( () => Array.apply(null, 
    Array(x)).map(() => 0) );
};

ArrayUtils.crop = function(array) {
  let top, bottom, left, right;
  
  top = 0;
  while (array[top] && array[top].every((e) => e === 0)) top += 1;
  
  bottom = array.length - 1;
  while (array[bottom] && array[bottom].every((e) => e === 0)) bottom -= 1;
  
  left = 0;
  while (array.every((e) => e[left] === 0)) left += 1;
  
  right = array[0].length - 1;
  while (array.every((e) => e[right] === 0)) right -= 1;
  
  let result;
  
  if (bottom < 0 || right < 0 ||
        top >= array.length || left >= array.length)
    result = [[]];
  else
    result = array.slice(top, bottom + 1)
        .map((line) => line.slice(left, right + 1));
  
  return result;
};

let Life = function(current = [[]]) {
  this.current = current;

  this.neighbourhood = [
    [-1, -1], [0, -1], [1, -1],
    [-1,  0],          [1,  0],
    [-1,  1], [0,  1], [1,  1]
  ];
  
    //           (-1) : Death; (0) : Same; (1) : Alive
  //             0,  1,  2,  3,  4,  5,  6,  7,  8
  this.rules = [-1, -1,  0,  1, -1, -1, -1, -1, -1];
}

Life.prototype.next = function(generations = 1) {
  let count = 0;
  
  while (count !== generations) {
    let [width, height] = [this.current[0].length, this.current.length];
    let next = ArrayUtils.getSquare(width + 2, height + 2);
    
    for (let row = 0; row < next.length; row++)
      for (let column = 0; column < next[0].length; column++) {
        let neighbours = this.neighbourhood.reduce((sum, [x, y]) => {
          let result = (this.current[row + y - 1]) ? 
            this.current[row + y - 1][column + x - 1] : undefined;
          return (result) ? sum + result : sum;
        }, 0);
    
        let rule = this.rules[neighbours];
        next[row][column] = (rule === -1) ? 0 
          : ((rule === 1) ? 1 
          : ((this.current[row - 1]) 
          ? ((this.current[row - 1][column - 1]) 
            ? this.current[row - 1][column - 1] : 0 ) 
          : 0)); 
      }
      
    this.current = ArrayUtils.crop(next);
  
    count += 1;
  }
  
  return this.current;
}

let getGeneration = (cells, generations) => (new Life(cells)).next(generations);