Javascript 使用browserify创建小部件

我正在做nodeschool的browserify冒险教程。其中一个练习涉及创建一个简单的小部件，该小部件将html字符串转换为DOM元素，将给定名称插入其中，然后将其附加到文档中选定的目标。有效的解决方案如下所示：

var domify = require('domify');
var html = '<div>Hello <span class="name"></span>!</div>';

module.exports = Widget;

function Widget() {
    if (!(this instanceof Widget)) return new Widget;
    this.element = domify(html);

    this.setName = function(str) {
        this.element.querySelector("span.name").textContent=str;
    }

    this.appendTo = function(target) {
        target.appendChild(this.element);
    }
}

如果没有它，我在浏览器中

Uncaught TypeError: Cannot read property 'setName' of undefined
    at Object.3.shoe (bundle.js:2397)
    at s (bundle.js:1)
    at e (bundle.js:1)
    at bundle.js:1

Uncaught TypeError: Cannot read property 'setName' of undefined
    at Object.3.shoe (bundle.js:2397)
    at s (bundle.js:1)
    at e (bundle.js:1)
    at bundle.js:1