If element does not have parent with specific class

if($(".myElem").parent().hasClass(".myDiv")) {
    console.log("has a parent with the class .myDiv")
}
else
{
    console.log("no parent class .myDiv found")
}

Use length to check it there are elements in the selector, and closest() would be better than parents() as it stops once it finds a match:

if(! $(".myElem").closest(".myDiv").length ) {
    console.log("has no parent with the class .myDiv")
}

If you are testing whether the element with class myElem has a direct parent with class myDiv use the following test

if(!$(".myElem").parent().hasClass("myDiv")) {
    console.log("test")
};