我使用watch（）的方式有什么问题？

Question

makeRow : function() {
            this.rowDiv = Y.Node.create("<div/>").addClass('rowDiv'),//.set('id', i),
            this.rowUL = Y.Node.create("<ul/>").addClass('rowUL'),
            this.handle = Y.Node.create("<li/>").addClass('handle'),
            this.plusImg = Y.Node.create("<img/>").set('src', 'images/plus.png').addClass('plus'),
            this.between = Y.Node.create("<div/>").addClass('between'),
            this.rowDel = Y.Node.create("<img/>").addClass('rowDel').set('src', 'images/redx.png'),
            this.rowDelLI = Y.Node.create("<li/>").addClass('delLI'),
            this.expand = Y.Node.create("<li/>").addClass('expand').set('innerHTML', 'expand?');


        this.rowUL.append(this.handle);
        this.rowUL.append(this.expand);
        this.rowDelLI.append(this.rowDel);
        this.rowDiv.append(this.rowDel);
        this.between.append(this.plusImg);
        this.rowDiv.append(this.rowUL);
        this.rowDiv.append(this.between);

        this.expanded = false;
        this.phrases = [];
        this.hiddenPhrases = [];

        //When I print this.rowDiv it returns the id, so hopefully I can treat this as a string of the id
        this.rowDiv.parentMakeRow = this;
        this.id = "<Object makeRow: id=" + id++ +">";

        this.watch("rowUL", function(id, oldval, newval){
            console.log('changed');
        });

        this.toString = function() {
            return this.id;
        }

是因为我使用文字符号吗？是因为这是封闭的吗？

我收到错误Uncaught TypeError：Object [object Object]没有方法＆＃39; watch＆＃39;

知道发生了什么事吗？