Check if element appended already w/ jQuery

I need to modify a function. When a condition is met an element is appended. I need to add a check to see if this element has been already added, because it can be only added just once.

function checkBox()
{
 if ($("#myBox").find('.myClas开发者_开发技巧s').length == 0)
 {
   $("#myBox").append(
        $('<a href="" id="newBox">click</a>')
   );   
 } 
}

function checkBox() {
    if (!$("#myBox").find('.myClass').length) {
        $("#myBox").append('<a href="" id="newBox">click</a>');
    }
}

Check working example http://jsfiddle.net/nYbTv/

function checkBox()
{
 if ($("#myBox").find('#newBox').length == 0)
 {
   $("#myBox").append(
        $('<a href="" id="newBox">click</a>')
   );   
 } 
}

Also note that when passing a serialised HTML string to append(), you don't have to rewrap it with the jQuery object.