$.parseXML()不使用没有根节点的xml字符串

Below is my code

下面是我的代码

 var str = "<single><n>Q1</n><v></v><m></m></single>
            <single><n>Q2</n><v>y</v><m></m></single>
            <single><n>Q3</n><v></v><m>y</m></single>";  
 // ! I gave this string value in three lines just for readability purpose

 var xmlDoc = $.parseXML( str );

 var xml = $(xmlDoc);

 alert(xml.find('single').size());  
 var str = "<sing