flowing text for cocos2d-js labels

flow_label.js

var HelloWorldLayer = cc.Layer.extend({
    sprite:null,
    ctor:function () {
        this._super();

        var size = cc.director.getWinSize();

        var helloLabel = new FlowLabel(100, "Lorem ipsum dolor sit amet, consectetur adipisicing elit.", "Arial", 24);
        helloLabel.x = size.width / 2;
        helloLabel.y = size.height / 2;
        this.addChild(helloLabel, 5);
        return true;
    }
});




var FlowLabel = cc.LabelTTF.extend({
    _flowText: null,
    ctor: function (textSpeed, text, fontName, fontSize, dimensions, hAlignment, vAlignment) {
        this._textSpeed = textSpeed;
        this._super('', fontName, fontSize, dimensions, hAlignment, vAlignment);
        this.setString(text);
    },
    setString: function(text){
        this._flowText = text;
        this.runAction(cc.actionTween(this._flowText.length * this._textSpeed * 0.001, "flowOffset", 0, this._flowText.length));
    },
    updateTweenAction: function(value, key){
        if(key == 'flowOffset'){
            cc.LabelTTF.prototype.setString.call(this, this._flowText.substring(0, value));
        }
    }
});

var HelloWorldScene = cc.Scene.extend({
    onEnter:function () {
        this._super();
        var layer = new HelloWorldLayer();
        this.addChild(layer);
    }
});