check element exist on page or not jquery code example

Example 1: jquery for element which doesnt exist on page load

$('body').on('click', '.my_class', function(event) { ...

Example 2: jquery check if element still exists

$(function() {
    var $button = $(".the_button");
    alert (isStale($button));
    $button.remove();
    alert (isStale($button));
});
    
function isStale($elem)
{
    return $elem.closest("body").length > 0;
};