game-of-life.js

class Cell {
  constructor(alive) {
    this.alive = alive;
  }

  toggle() {
    this.alive = !this.alive;
  }

  copy() {
    return new Cell(this.alive);
  }
}

class Universe {
  constructor(width, height) {
    this.width = width;
    this.height = height;

    this.cells = _.range(width * height).map((i) => {
      return (i % 2 === 0 || i % 7 === 0)
        ? new Cell(true)
        : new Cell(false);
    });
  }

  index(row, col) {
    return (row * this.height + col);
  }

  liveNeighborCount(row, col) {
    let count = 0;
    const rowDeltas = [
      this.height - 1, 0, 1,
    ];
    const colDeltas = [
      this.width - 1, 0, 1,
    ];

    for (rowDelta in rowDeltas) {
      for (colDelta in colDeltas) {
        if (rowDelta === 0 && colDelta === 0) {
          continue;
        }

        const neighborRow = (row + rowDelta) % this.height();
        const neighborCol = (col + colDelta) % this.width();
        const index = this.index(neighborRow, neightborCol);

        // cast as bool by adding
        count += this.cells()[index];
      }
    }
    return count;
  }

  tick() {
    const nextCells = this.cells.map((cell) => cell.copy())

    for (let row = 0; row < self.height; row ++) {
      for (let col = 0; col < self.width; col++) {
        const index = this.index(row, col);
        const cell = this.cells[index];
        const neighborCount = this.liveNeighborCount(row, col);

        let nextLife = cell.alive;
        if (cell.alive) {
          if (neighborCount < 2) {
            nextLife = false;
          } else if (neighborCount > 3) {
            nextLife = false;
          }
        } else {
          if (neighborCount === 3) {
            nextLife = true;
          }
        }

        nextCells[index] = new Cell(nextLife);
      }
    }

    this.cells = nextCells;
  }
}