Fire event when div is visible to visitor with jQuery?

Question

The function: I want to change the class of a certain item when a user see a certain div (scrolls down to it).

How I do it now: I\'

Answer 1

By looking at the source code of the jquery-appear plugin, it is possible to pass the argument one, to fire the event one time only (one: true), or every time it appears (one: false)

$('#myDiv').appear(function() {
    $("#aDiv").addClass("active");
}, {
    one: false
});