by-idb/snake.js

A simple terminal snake game library with no external dependencies

class Snake {
    constructor(width, height) {
        this.width = width;
        this.height = height;
        this.reset();
    }

    reset() {
        // Initialize snake position in the center
        const startX = Math.floor(this.width / 2);
        const startY = Math.floor(this.height / 2);
        this.body = [
            { x: startX, y: startY },
            { x: startX - 1, y: startY },
            { x: startX - 2, y: startY }
        ];
        this.direction = 'right';
        this.nextDirection = 'right';
    }

    move(food) {
        // Update direction
        this.direction = this.nextDirection;

        // Get head position
        const head = { ...this.body[0] };

        // Move head based on direction
        switch (this.direction) {
            case 'up':
                head.y--;
                break;
            case 'down':
                head.y++;
                break;
            case 'left':
                head.x--;
                break;
            case 'right':
                head.x++;
                break;
        }

        // Check if food is eaten
        const ateFood = head.x === food.x && head.y === food.y;

        // Add new head to the beginning of body array
        this.body.unshift(head);

        // Remove tail if no food was eaten
        if (!ateFood) {
            this.body.pop();
        }

        return ateFood;
    }

    changeDirection(newDirection) {
        // Prevent 180-degree turns
        const opposites = {
            'up': 'down',
            'down': 'up',
            'left': 'right',
            'right': 'left'
        };

        if (opposites[newDirection] !== this.direction) {
            this.nextDirection = newDirection;
        }
    }

    checkCollision() {
        const head = this.body[0];

        // Check wall collision
        if (
            head.x < 0 ||
            head.x >= this.width ||
            head.y < 0 ||
            head.y >= this.height
        ) {
            return true;
        }

        // Check self collision
        for (let i = 1; i < this.body.length; i++) {
            if (head.x === this.body[i].x && head.y === this.body[i].y) {
                return true;
            }
        }

        return false;
    }
}

module.exports = Snake;