How to add a delay to CSS Vertical Dropdown Menu

问题:

I am needing to add a delay to the mouseover event of my dropdown menu so that if someone mouses over the menu going to another link on page the menu will not drop down instantly. Thanks for your help.

http://jsfiddle.net/cgagliardi/NPVVQ/

回答1:

You can add a setTimeout() to delay the show(), and on hover out clear the timeout so that if the user moves the mouse out before the delay is up it will be cancelled. And you can encapsulate that in your own jQuery plugin:

jQuery.fn.hoverWithDelay = function(inCallback,outCallback,delay) {
    this.each(function(i,el) {
        var timer;
        $(this).hover(function(){
           timer = setTimeout(function(){
              timer = null;
              inCallback.call(el);
           }, delay);
        },function() {
           if (timer) {
              clearTimeout(timer);
              timer = null;
           } else
              outCallback.call(el);
        });
    });
};

Which you can use like this:

$('ul.top-level li').hoverWithDelay(function() {
    $(this).find('ul').show();
}, function() {
    $(this).find('ul').fadeOut('fast', closeMenuIfOut);
}, 500);

I cobbled that plugin together in a hurry so I'm sure it could be improved, but it seems to work in this updated version of your demo: http://jsfiddle.net/NPVVQ/3/

As far as explaining how my code works: the .each() loops through all the elements in the jQuery object that the function is called on. For each element a hover handler is created that uses setTimeout() to delay calling the callback function provided - if the mouseleave occurs before the time is up this timeout is cleared so that the inCallback is not called. The .call() method is used on inCallback and outCallback to set the right value for this.

回答2:

You can use CSS3 Animation or Transition.

http://www.css3maker.com/css3-animation.html

http://www.css3maker.com/css3-transition.html

Or you can handle timeouts in Javascript, I think a easy way is to attach a setTimeout before show(); and use clearTimeout on mouseleave event

回答3:

I updated the code now your menu comes after 1/2 sec. Demo

$('#navigation').show(2000);

This is enough to delay the animation....of show() in jquery.

I just used another div to pause the animation you can see it.