(function($) {
$.fn.random = function(selector) {
debugger;
var elems = selector ? this.filter(selector) : this;
var len = elems.length;
var i = Math.floor(Math.random() * len);
var elem = elems.eq(i);
console.log(len, i, elem);
returnthis.pushStack(elem);
};
}(jQuery));