jquery Inheritance Extend usage

/直接基于jQuery的扩展,判断是否为空 $.isBlank = function (obj){    return ( typeof (obj)== ‘undefined‘ ||obj== ‘‘ ||obj== null );   } //直接基于jQuery的扩展，去除html标签，保留内容   $.htmlContent = function (tag){    var reTag = /<(?:.|\s)*?>/g;    return tag.replace(reTag, "" );   } //直接基于jQuery的扩展(方式二) $.xy = { sayhello: function (){ return "hello" ;}, saybaybay: function (){ return "baybay" ;} }; //jQuery类级别的扩展 $.extend({ add: function (a,b){ return a+b;}, diff: function (a,b){ return a-b} }); //jQuery对象级别的扩展 $.fn.extend({   getvalue: function (){   return this .val();    }   }); HTML code < body >   < script type = "text/javascript" >    document.write("判断是否为空："+$.isBlank(null));   </ script >   < span class = "myspan" ></ span >   < script type = "text/javascript" >    document.write("过滤html标签："+$.htmlContent("< html >< body >< a id = ‘a1‘ >a标签</ a >< div style = ‘width:100%‘ >div标签</ div >内容</ body ></ html >")+"< br />");    document.write("扩展自jQuery类的xy的sayhello方法："+ $.xy.sayhello()+"</ br >");    document.write("扩展自jQuery类的xy的sayhello方法："+ $.xy.saybaybay()+"</ br >");    document.write("基于jQuery类的add法："+ $.add(3,5)+"</ br >");    document.write("基于jQuery类的diff法："+ $.diff(5,3)+"</ br >");    document.write("基于自jQuery类对象的扩展getvalue()："+$("< input type = ‘text‘ value = ‘str‘ />").getvalue()+"< br />");   </ script >   </ body >

jquery Inheritance Extend usage