JavaScript实现带音符反馈的导航栏交互效果

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>音乐导航</title>
 <style>
 * {
  margin: 0;
  padding: 0;
  list-style: none;
  border: 0;
 }
 #nav {
  width: 706px;
  height: 40px;
  border: 1px solid #ccc;
  margin: 100px auto;
  overflow: hidden;
 }
 #nav ul {
  width: 710px;
 }
 #nav ul li {
  float: left;
  width: 100px;
  text-align: center;
  line-height: 40px;
  border-right: 1px dashed #ccc;
  position: relative;
 }
 #nav ul li a { /* a 标签填充整个 li */
  width: 100%;
  height: 100%;
  display: inline-block;
 }
 a {
  text-decoration: none;
  color: #000000;
 }
 span {
  width: 100px;
  height: 40px;
  background: skyblue;
  position: absolute;
  left: 0;
  top: 40px;
  z-index: -1;
 }
 </style>
</head>
<body>
 <nav id="nav">
 <ul id="ul">
  <li><a href="">千千音乐</a><span></span><audio src=" source/a1.mp3"></audio></li>
  <li><a href="">echo回声</a><span></span><audio src=" source/a2.mp3"></audio></li>
  <li><a href="">酷狗音乐</a><span></span><audio src=" source/a3.mp3"></audio></li>
  <li><a href="">QQ音乐</a><span></span><audio src=" source/a4.mp3"></audio></li>
  <li><a href="">酷我音乐</a><span></span><audio src=" source/a5.mp3"></audio></li>
  <li><a href="">网易云音乐</a><span></span><audio src=" source/a6.mp3"></audio></li>
  <li><a href="">虾米音乐</a><span></span><audio src=" source/a7.mp3"></audio></li>
 </ul>
 </nav>
<script src="js/myFunc.js"></script>
<script>
 window.onload = function () {
 // 1.获取标签
 var ul = $("ul");
 var allLis = ul.children;

 // 2.监听鼠标进入 li 标签
 for(var i=0; i<allLis.length; i++){
  allLis[i].onmouseover = function () {
  // 2.1 缓动动画
  buffer(this.children[1], {"top": 0});

  // 2.2 播放音符
  this.children[2].play();
  this.children[2].currentTime = 0;
  };

  // 2.3 监听鼠标离开
  allLis[i].onmouseout = function () {
  buffer(this.children[1], {"top": 40});
  };

  // 3.监听键盘的点击(1-7分别代表 do re mi fa so la xi)
  document.onkeydown = function (event) {
  var e = event || window.event;
  // console.log(e.keyCode);

  var keyCode = e.keyCode -49;
  buffer(allLis[keyCode].children[1], {"top": 0}, function () {
   buffer(allLis[keyCode].children[1], {"top": 40})
  })

  // 2.2 播放音符
  allLis[keyCode].children[2].play();
  allLis[keyCode].children[2].currentTime = 0;
  }
 }
 }
</script>
</body>
</html>

function $(id) {
 return typeof id === "string" ? document.getElementById(id) : null;
}

/**
 * 缓动动画函数
 * @param obj
 * @param json
 * @param fn
 */
function buffer(obj, json, fn) {
 // 1.1 清除定时器
 clearInterval(obj.timer);

 // 1.3 设置定时器
 var begin = 0, target = 0, speed = 0;
 obj.timer = setInterval(function () {
 // 1.3.0 标记
 var flag = true;
 for(var k in json){
  // 1.3.1 求出初始值
  if("opacity" === k){ // 透明度
  console.log(getCssStyleAttr(obj, k));
  begin = Math.round(parseFloat(getCssStyleAttr(obj, k)) * 100) || 100; // 获取 CSS 样式值
  target = parseInt(json[k] * 100);
  }else if("scrollTop" === k){
  begin = Math.ceil(obj.scrollTop);
  target = parseInt(json[k]);
  }else { // 其他情况
  begin = parseInt(getCssStyleAttr(obj, k)) || 0; // 获取 CSS 样式值
  target = parseInt(json[k]);
  }
  // console.log(begin, target);

  // 1.4 求出步长
  // 缓动动画原理：盒子本身的位置 + 步长（不断变化的，由大变小）
  // 步长：begin = begin + (end - begin) * 缓动系数
  speed = (target - begin) * 0.2;

  // 1.6 判断是否向上取整
  speed = (target > begin) ? Math.ceil(speed) : Math.floor(speed);

  // 1.5 移动起来
  if("opacity" === k){ // 透明度
  // w3c 的浏览器
  obj.style.opacity = (begin + speed) / 100;
  // ie
  obj.style.filter = "alpha(opacity=" + (begin + speed) +")";
  }else if("scrollTop" === k){
  obj.scrollTop = begin + speed;
  }else {
  obj.style[k] = begin + speed + "px";
  }


  // 1.7 判断
  if(begin !== target){
  flag = false;
  }
 }
 // 1.8 清除定时器
 if(flag){
  clearInterval(obj.timer);

  // 判断有没有回调函数
  if(fn){
  fn()
  }
 }
 }, 20)
}