实现不支持所请求的对象或操作类型。

Question

我上课“世界”和“墙”

function World() {

 this.map = new Array();


 this.createWorld = function(mapArray, ctx) {
    console.log(mapArray.length);
    for (var i = 0; i < mapArray.length; i++) {
        obj = new Wall(mapArray[i, 0], mapArray[i, 1], mapArray[i, 2], mapArray[i, 3]);
        //img = obj.createImg(ctx)
        this.map.push(obj);
    };
    //return img;
 }

 this.getItem = function(i) {
    return this.map[i];
 }
 this.getSize = function() {
    return this.map.length;
 }
}
function Wall(x, y, height, width) {

 this.x = x;
 this.y = y;
 this.height = height;
 this.width = width;


 this.createImg = function(ctx) {

    ctx.fillStyle = "rgb(166, 175, 179)";
    ctx.fillRect(this.x, this.y, this.height, this.width);

    return ctx.getImageData(0, 0, this.height, this.width);
 }

 //get
 this.getX = function() {
    return this.x;
 }
 this.getY = function() {
    return this.y;
 }
 this.getHeight = function() {
    return this.height;
 }
 this.getWidth = function() {
    return this.width;
 }

 //set
 this.setX = function(value) {
    this.x = value;
 }

 this.setY = function(value) {
    this.y = value;
 }
}

当我在主程序中尝试获取Item Wall时，出现错误：Uncaught NotSupportedError：实现不支持所请求的对象或操作类型。 我的错误在哪里？