Add custom method to DOM-Element via jQuery

custom-object-method.js

/**
 * improved version of https://stackoverflow.com/a/22649723
 *
 * function is bound to DOM-Element and can even used, when you load the "menu"
 * via another jQuery selector later in code
 */

// Binds the function to each DOM-Element matching my selector
const $menu = $('.my-popup').each(function(i) {
    /**
     * @param {boolean} state If true (or omitted) it opens the window otherwise it closes
     */
    this.open = function (state = true) {
        this.dataset.isOpen = state ? 1 : 0;
        $(this).toggle( display );
    };
    this.close = function () {
        this.open(false);
    };
});


// to call the function (even if you dont have access to the Original jQuery variable
$('.my-popup')[0].open();
$('.my-popup')[0].close()