attr()-jQueryメソッド

<button class="olive button1">button1 olive</button>
</br>
<button class="olive button2">button2 olive</button>

button{
  width:300px;
  height:60px;
}
.olive{
  background-color:olive;
}
.orange{
  background-color:orange;
}

var $arg = $('button.button1').attr('class');
document.write($arg + ';');
var $arg2 = $('button.button2').attr('class','orange');
document.write($arg2[0]);