Please try this.
<table id="dg" title="My Users" class="easyui-datagrid" style="width:700px;height:250px"
data-options="
url:'get_users.php',
toolbar:'#toolbar',
pagination:true,
rownumbers:true,
fitColumns:true,
singleSelect:true,
onDblClickRow:function(){
editUser();
}
">
...
</table>