js 小白问个小问题希望各位大牛指点下迷津

index.js
define(function() {

function Window() {

}

Window.prototype = {

    //window 事件
    windowscreen: function(id) {
        //window.onload = this.getHeight(options);
        var that = this;
        window.onresize = function(id) {
                that.getHeight(id);
               //执行 onresize 函数的时候浏览器报错
               // index.js:32 Uncaught TypeError: Cannot read property 'style' of null
        }
        setInterval(this.getHeight(id), 1000);
    },
    //获取屏幕高度让指定元素垂直居中
    getHeight: function(id) {
        var oDiv = document.getElementById(id),
            screenHeight = document.documentElement.clientHeight;
            oDiv.style.marginTop = (parseInt(screenHeight / 2)) + 'px';
    }
}
return {
    Window: Window
};

});

这是另外一个 js 文件 main.js-- require.config({ paths:{ "jquery": "jquery.min" } })

require(['jquery','index'],function($,i) { var getHeight = new i.Window(); // getHeight.getHeight('header'); // getHeight.getHeight('main'); // getHeight.getHeight('bottom'); getHeight.getHeight('header'); getHeight.windowscreen('header'); })

第一次接触这种写法想学习学习...处处都是坑....- -。希望大牛能够指点下我这个小白....该怎么样修改才行啊...