JS原生带缩略图的图片切换效果

本例中用到的 moveElement(elementID,final_x,final_y,interval)是来自《JavaScript DOM编程艺术（中文第二版）》一书第10章中有一段代码。（可以直接baidu）

左边是banner图，右边是缩略图，当鼠标滑入缩略图时，也会切换图片。

一、这段是html代码，可以直接拷贝，需要自己准备相同大小的banner图，例中图片都是500x300

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>图片轮播</title>
  <script src="./js.js"></script>
  <style>
    * {
      margin: 0;
      padding: 0;
      word-break: break-all;
    }
    body {
      background: #FFF;
      color: #333;
      font: 12px/1.6em Helvetica, Arial, sans-serif;
    }
    a {
      color: #0287CA;
      text-decoration: none;
    }
    a:hover {
      text-decoration: underline;
    }
    ul,
    li {
      list-style: none;
    }
    fieldset,
    img {
      border: none;
    }
    legend {
      display: none;
    }
    em,
    strong,
    cite,
    th {
      font-style: normal;
      font-weight: normal;
    }
    input,
    textarea,
    select,
    button {
      font: 12px Helvetica, Arial, sans-serif;
    }
    table {
      border-collapse: collapse;
    }
    html {
      overflow: -moz-scrollbars-vertical;
    }
    #ifocus {
      width: 620px;
      height: 320px;
      margin: 20px;
      border: 1px solid #DEDEDE;
      background: #F8F8F8;
    }
    #ifocus_pic {
      display: inline;
      position: relative;
      float: left;
      width: 500px;
      height: 300px;
      overflow: hidden;
      margin: 10px 0 0 10px;
    }
    #ifocus_piclist {
      position: absolute;
    }
    #ifocus_piclist li {
      width: 500px;
      height: 300px;
      overflow: hidden;
    }
    #ifocus_piclist img {
      width: 500px;
      height: 300px;
    }
    #ifocus_btn {
      display: inline;
      float: right;
      width: 94px;
      margin: 9px 9px 0 0;
    }
    #ifocus_btn li {
      width: 94px;
      height: 57px;
      cursor: pointer;
      opacity: 0.5;
      -moz-opacity: 0.5;
      filter: alpha(opacity=50);
    }
    #ifocus_btn img {
      width: 80px;
      height: 50px;
      margin: 7px 0 0 11px;
    }
    #ifocus_btn .current {
      /* background: url(i/ifocus_btn_bg.gif) no-repeat; */
      opacity: 1;
      -moz-opacity: 1;
      filter: alpha(opacity=100);
    }
  </style>
</head>
<body>
  <div id="ifocus">
    <div id="ifocus_pic">
      <div id="ifocus_piclist" style="left:0; top:0;">
        <ul>
          <li><a href="#"><img src="./images/1.jpg" alt="" /></a></li>
          <li><a href="#"><img src="./images/2.jpg" alt="" /></a></li>
          <li><a href="#"><img src="./images/3.jpg" alt="" /></a></li>
          <li><a href="#"><img src="./images/4.jpg" alt="" /></a></li>
          <li><a href="#"><img src="./images/5.jpg" alt="" /></a></li>
        </ul>
      </div>
    </div>
    <div id="ifocus_btn">
      <ul>
        <li class="current"><img src="./images/1.jpg" alt="" /></li>
        <li><img src="./images/2.jpg" alt="" /></li>
        <li><img src="./images/3.jpg" alt="" /></li>
        <li><img src="./images/4.jpg" alt="" /></li>
        <li><img src="./images/5.jpg" alt="" /></li>
      </ul>
    </div>
  </div>
</body>
</html>

二、这段是js代码，其中用到了几个经典的js代码。在js中需要修改对应的id名字、图片移动的尺寸等。

function $(id) {
  return document.getElementById(id);
}
function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function () {
      oldonload();
      func();
    }
  }
}
function moveElement(elementID, final_x, final_y, interval) {
  if (!document.getElementById) return false;
  if (!document.getElementById(elementID)) return false;
  var elem = document.getElementById(elementID);
  if (elem.movement) {
    clearTimeout(elem.movement);
  }
  if (!elem.style.left) {
    elem.style.left = "0px";
  }
  if (!elem.style.top) {
    elem.style.top = "0px";
  }
  var xpos = parseInt(elem.style.left);
  var ypos = parseInt(elem.style.top);
  if (xpos == final_x && ypos == final_y) {
    return true;
  }
  if (xpos < final_x) {
    var dist = Math.ceil((final_x - xpos) / 10);
    xpos = xpos + dist;
  }
  if (xpos > final_x) {
    var dist = Math.ceil((xpos - final_x) / 10);
    xpos = xpos - dist;
  }
  if (ypos < final_y) {
    var dist = Math.ceil((final_y - ypos) / 10);
    ypos = ypos + dist;
  }
  if (ypos > final_y) {
    var dist = Math.ceil((ypos - final_y) / 10);
    ypos = ypos - dist;
  }
  elem.style.left = xpos + "px";
  elem.style.top = ypos + "px";
  var repeat = "moveElement('" + elementID + "'," + final_x + "," + final_y + "," + interval + ")";
  elem.movement = setTimeout(repeat, interval);
}
function classNormal(iFocusBtnID) {
  var iFocusBtns = $(iFocusBtnID).getElementsByTagName('li');
  for (var i = 0; i < iFocusBtns.length; i++) {
    iFocusBtns[i].className = 'normal';
  }
}
function classCurrent(iFocusBtnID, n) {
  var iFocusBtns = $(iFocusBtnID).getElementsByTagName('li');
  iFocusBtns[n].className = 'current';
}
function iFocusChange() {
  if (!$('ifocus')) return false;
  $('ifocus').onmouseover = function () {
    atuokey = true
  };
  $('ifocus').onmouseout = function () {
    atuokey = false
  };
  var iFocusBtns = $('ifocus_btn').getElementsByTagName('li');
  var listLength = iFocusBtns.length;
  iFocusBtns[0].onmouseover = function () {
    moveElement('ifocus_piclist', 0, 0, 5);
    classNormal('ifocus_btn');
    classCurrent('ifocus_btn', 0);
  }
  if (listLength >= 2) {
    iFocusBtns[1].onmouseover = function () {
      moveElement('ifocus_piclist', 0, -300, 5);
      classNormal('ifocus_btn');
      classCurrent('ifocus_btn', 1);
    }
  }
  if (listLength >= 3) {
    iFocusBtns[2].onmouseover = function () {
      moveElement('ifocus_piclist', 0, -600, 5);
      classNormal('ifocus_btn');
      classCurrent('ifocus_btn', 2);
    }
  }
  if (listLength >= 4) {
    iFocusBtns[3].onmouseover = function () {
      moveElement('ifocus_piclist', 0, -900, 5);
      classNormal('ifocus_btn');
      classCurrent('ifocus_btn', 3);
    }
  }
  if (listLength >= 5) {
    iFocusBtns[4].onmouseover = function () {
      moveElement('ifocus_piclist', 0, -1200, 5);
      classNormal('ifocus_btn');
      classCurrent('ifocus_btn', 4);
    }
  }
}
setInterval('autoiFocus()', 3000);
var atuokey = false;
function autoiFocus() {
  if (!$('ifocus')) return false;
  if (atuokey) return false;
  var focusBtnList = $('ifocus_btn').getElementsByTagName('li');
  var listLength = focusBtnList.length;
  for (var i = 0; i < listLength; i++) {
    if (focusBtnList[i].className == 'current') var currentNum = i;
  }
  if (currentNum == 0 && listLength != 1) {
    moveElement('ifocus_piclist', 0, -300, 5);
    classNormal('ifocus_btn');
    classCurrent('ifocus_btn', 1);
  }
  if (currentNum == 1 && listLength != 2) {
    moveElement('ifocus_piclist', 0, -600, 5);
    classNormal('ifocus_btn');
    classCurrent('ifocus_btn',2);
  }
  if (currentNum == 2 && listLength != 3) {
    moveElement('ifocus_piclist', 0, -900, 5);
    classNormal('ifocus_btn');
    classCurrent('ifocus_btn',3);
  }
  if (currentNum == 3) {
    moveElement('ifocus_piclist', 0, -1200, 5);
    classNormal('ifocus_btn');
    classCurrent('ifocus_btn', 4);
  }
  if (currentNum == 4) {
    moveElement('ifocus_piclist', 0, 0, 5);
    classNormal('ifocus_btn');
    classCurrent('ifocus_btn',0);
  }
}
addLoadEvent(iFocusChange);

效果如下图

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总结

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