Generate a grid with a random path

buildMapWithPath.js

function buildMapWithPath(H, W, L) {
    let A = [], p = [0,0];
    for (let Y = 0; Y < H; Y++) {
        A[Y] = [];
        for (let X = 0; X < W; X++) {
            A[Y].push(0);
        }
    }
    function mark(p) { 
        A[p[0]][p[1]] = 1; 
    }
    function getPos(y, x) {
        if (y < H && y > -1 && x < W && x > -1) {
            return A[y][x];
        }
        return false;
    }
    function getTouches(pVar) {
        let pos = [[0,1],[-1,1],[-1,0],[-1,-1],[0,-1],[1,-1],[1,0],[1,1]];
        return pos.reduce(function (c, b) {
            if (getPos(pVar[0]+b[0], pVar[1]+b[1]) == 1) {
                c=c+1;
            }
            return c;
        }, 0);
    }
    function getPossible(pVar) {
        var pos = [[0,1],[-1,0],[1,0],[0,-1]];
        return pos.reduce(function (arr, b) {
            let newPos = getPos(pVar[0] + b[0], pVar[1] + b[1]);
            if (!newPos) {
                newPos = [pVar[0] + b[0], pVar[1] + b[1]];
                if (getTouches(newPos) <= 2) {
                    if (newPos[0] > -1 && newPos[1] > -1 && newPos[0] < H && newPos[1] < W) {
                        arr.push(newPos);
                    }
                }
            }
            return arr;
        }, []);
    }
    p[0] = Math.floor(Math.random()*p.length);
    mark(p);
    for (var I = 0; I < L; I++) {
        p = getPossible(p);
        p = p[Math.floor(Math.random()*p.length)];
        mark(p);
    }
    return A;
}

// map = buildMapWithPath(20,20, 40);