这几句jQuery代码看不懂，求解，谢谢！！！！！！！
程序代码：<script type="text/javascript">
(function($,sr){
var debounce = function (func, threshold, execAsap) {
var timeout;
return function debounced () {
var obj = this, args = arguments;
function delayed () {
if (!execAsap)
func.apply(obj, args);
timeout = null;
};
if (timeout)
clearTimeout(timeout);
else if (execAsap)
func.apply(obj, args);
timeout = setTimeout(delayed, threshold || 100);
};
}
jQuery.fn[sr] = function(fn){ return fn ? this.bind('resize', debounce(fn)) : this.trigger(sr); };
})(jQuery,'smartresize');
</script>
特别是这句，jQuery.fn[sr] = function(fn){ return fn ? this.bind('resize', debounce(fn)) : this.trigger(sr); };
jQuery.fn[sr] 是什么意思，谢谢！！
