JavaScript继承，覆盖行为

Question

这可能是一个冗长的文章。我必须即时学习JS，可能会犯简单的错误。

我正在用JS/HTML编写游戏，并且正在使用EasyStar为某些实体进行一些探索行为。我正在使用继承将下面Walker4中概述的行为提供给多个实体，底部的一个例子：

function Walker4(game, img, Ai, lX, lY) {
    this.easyStar = Ai;
    this.dX = 0;
    this.dY = -1;
    this.animation = [];
    this.animation["NE"] = null;
    this.animation["NW"] = null;
    this.animation["SE"] = null;
    this.animation["SW"] = null;
    this.currAnimation = null;
    this.facing = "";
    this.img = img;
    this.isWalking = false;
    this.isFindingPath = false;
    this.destX = null;
    this.destY = null;
    this.path = [];
    this.next = null;
    this.loadCount = 0;
    Entity.call(this, game, lX, lY);
}
Walker4.prototype = new Entity();
Walker4.prototype.constructor = Walker4;
Walker4.prototype.update = function () {
    if (this.isFindingPath) return;
    if (this.isWalking) this.walkPath();
    if (this.destX != null && this.destY != null) {
        this.isFindingPath = true;
        that = this;
        easyStar.findPath(this.x, this.y, this.destX, this.destY, function (path) {
            if (path === null) {
                console.log("No path :(");
            } else {
                console.log("Path! The first Point is " + path[0].x + " " + path[0].y);
                that.path = path;
                that.next = that.path.shift();
                that.isWalking = true;
            }
        });
        this.destX = null;
        this.destY = null;
        this.isFindingPath = false;
        easyStar.calculate();
    }
    Entity.prototype.update.call(this);
}
Walker4.prototype.walkPath = function () {
    if (this.path.length == 0) {
        if (Math.floor(this.x) == this.next.x && Math.floor(this.y) == this.next.y) {
            this.dX = 0;
            this.dY = 0;
        }
        isWalking = false;
        return;
    }
    if (Math.floor(this.x) == this.next.x && Math.floor(this.y) == this.next.y) {
        this.next = this.path.shift();
        this.dX = setDirection(Math.floor(this.x), this.next.x);
        this.dY = setDirection(Math.floor(this.y), this.next.y);
        this.currAnimation = this.animation[setFace(this.dX, this.dY)];
    }
    this.x += this.dX * this.game.clockTick * speed;
    this.y += this.dY * this.game.clockTick * speed;
}


Walker4.prototype.draw = function (ctx) {
    pt1 = twodtoisoX(this.x, this.y) + 27 - this.currAnimation.frameWidth / 2;
    pt2 = twodtoisoY(this.x, this.y) + 10 - this.currAnimation.frameHeight / 2;
    ctx.fillRect(pt1, pt2, 5, 5);
    //console.log(pt1, pt2);
    this.currAnimation.drawFrame(this.game.clockTick, ctx, pt1, pt2);
    Entity.prototype.draw.call(this);
}
//Cart Walkers 
function eCartMan(game, img, Ai, lX, lY) {
    Walker4.call(this, game, img, Ai, lX, lY);
    this.animation["NE"] = new Animation(img, 0, 0, 60, 48, 12, aSpeed, 12, true);
    this.animation["NW"] = new Animation(img, 0, 1, 60, 48, 12, aSpeed, 12, true);
    this.animation["SE"] = new Animation(img, 0, 2, 60, 48, 12, aSpeed, 12, true);
    this.animation["SW"] = new Animation(img, 0, 3, 60, 48, 12, aSpeed, 12, true);
    this.currAnimation = this.animation["NE"];
}
eCartMan.prototype = new Walker4();
eCartMan.prototype.constructor = eCartMan;

所有这些实体都添加到每个游戏tick中更新的实体列表中，每个实体分别为update和draw分别为调用。Easy Star似乎为每个实体提供了一条路径，但是只有最近添加的实体实际上才会遵循其给定的道路。我想念什么？

任何帮助。

Answer 1

好的，解决了问题。感谢@hmr的帮助。

最终在that = this;上出现了一个范围问题，并且每个Walker都需要自己的EasyStar Pathfinder版本。that成为全局，并打开了步行者的所有实例以相互修改。