Cocos2d-JS This 与 Layer 骚操作

起因：

想要简化几处重复的代码块，代码形如下图

    var xxxList = data.xxxList;
    if (!this.aaaLayer) {
        this.aaaLayer = new AAALayer(xxxList);
        this.aaaLayer.setAnchorPoint(0.5, 0.5);
        this.background.addChild(this.aaaLayer, 3);
    } else {
        this.aaaLayer.remove();
        this.aaaLayer.layout(xxxList);
    }
    if (!this.bbbLayer) {
        this.bbbLayer = new BBBLayer(xxxList);
        this.bbbLayer.setAnchorPoint(0.5, 0.5);
        this.background.addChild(this.bbbLayer, 3);
    } else {
        this.bbbLayer.remove();
        this.bbbLayer.layout(xxxList);
    }
    if (!this.cccLayer) {
        this.cccLayer = new CCCLayer(xxxList);
        this.cccLayer.setAnchorPoint(0.5, 0.5);
        this.background.addChild(this.cccLayer, 3);
    } else {
        this.cccLayer.remove();
        this.cccLayer.layout(xxxList);
    }
    if (!this.dddLayer) {
        this.dddLayer = new DDDLayer(xxxList);
        this.dddLayer.setAnchorPoint(0.5, 0.5);
        this.background.addChild(this.dddLayer, 3);
    } else {
        this.dddLayer.remove();
        this.dddLayer.layout(xxxList);
    }

由于重复度太高，看着实在难受，于是就想整合在一起，但是由于每个Layer都要对应一个构造Layer，通常会需要用条件判断来进行划分，但是这样以来难免又写的很长，所以我决定用两个数组分别存放目标Layer和构造器Layer,于是就有了下面的整合函数：

    compressFunc: function (xxxList) {
        var targetLayer = [
            "aaaLayer",
            "bbbLayer",
            "cccLayer",
            "dddLayer"
        ];

        var constructLayer = [
            AAALayer,
            BBBLayer,
            CCCLayer,
            DDDLayer
        ];

        targetLayer.forEach(function (item, index){
            this[item] = new constructLayer[index](xxxList[index].data);
            this[item].setAnchorPoint(0.5, 0.5);
            this.background.addChild(this[item], 3);
        }.bind(this));
    },

如此一来就可以完美的用forEach和this[item]来避免很长的条件判断了，鉴于平时我都不会用到this[xxx]这种结构，所以姑且记录下来，万一以后就变成了一个Bug呢