javascript命名空间的简单实现

<script>
(function(){
if(!window.JS){
window['JS'] = {}
}
var $ = function(id) {
return document.getElementById(id);
}
var html = function (id) {
if(!(obj = $(id))) return false;
alert($(id).innerHTML);
}
window['JS']['html'] = html;
})();
window.onload = function(){
JS.html('p');
}
</script>
<p id="p">content</p>

(function(){
if(typeof JS=== "undefined" || !JS) {
var JS= window.JS= {};
}
JS.util = {};
})();