javascript - 基于滚动高度的淡入/淡出

Question

我有以下应该在超过 1000 像素.secondLogo时出现（通过淡入）scrollToTop

var secondLogo = $(".secondLogo");
$(window).scroll(function(){
  //more then or equals to
  if($(window).scrollTop() >= 1000 ){
       secondLogo.fadeIn();

  //less then 1000px from top
  } else {
     secondLogo.fadeOut();

  }
});

HTML

<div class="secondLogo">
    <img src="images/smm_logo_large.png" alt="Student Makers Market logo"/>
</div>

CSS

.secondLogo{
    opacity:0;
    position:fixed;
    z-index:-10;
    top: 15%;
    left: 3%;
    opacity:0.1;
    filter:alpha(opacity=10); /* For IE8 and earlier */
}

Answer 1

$.fn.fadeIn并且$.fn.fadeOut不要操纵 css 属性opacity。display:none初始化你的元素

.secondLogo {
    display: none;
    position: fixed;
    z-index: -10;
    top: 15%;
    left: 3%;
}