Question

How to pass whats inside of tag with myClass class as a string here?

function przyciskRozpoczynajacyEdycje() { 
    var items = document.getElementsByClassName('myClass');
    for (var i=0;i<items.length;i++) {
        items[i].addEventListener("click", function () { passIdToEdit('How to put here whats inside tag with class "myClass"?') });
    }
}​

Answer 1

Did you try this.innerHTML? Inside an event handler this is the associated object of the event, in this case the HTML element:

items[i].addEventListener("click", function () {
    passIdToEdit(this.innerHTML);
});