这个貌似很简单吧var a = document.getElementById( 'a1' ).class;
document.getElementById( 'a1' ).class = document.getElementById( 'a2' ).class;
document.getElementById( 'a2' ).class = a;
document.getElementById( 'a1' ).class = document.getElementById( 'a2' ).class;
document.getElementById( 'a2' ).class = a;
document.getElementById('a1').ClassName = document.getElementById('a2').ClassName;
document.getElementById('a2').ClassName = tmp_Class;
var tmp =document.getElementById('a1').className;
document.getElementById('a1').className = document.getElementById('a2').className;
document.getElementById('a2').className = tmp;