JavaScript面向对象实现放大镜案例

<div class="small"> <img src="images/timg.jpg" alt=""> <span class="grayBox"></span></div><div class="big"> <img src="images/timg.jpg" alt=""></div>

.small { width: 400px; height: 400px; position: relative; border:4px solid #ddd; box-shadow: 0 0 5px rgba(0,0,0,.5);}.small img{ width: 100%; height: 100%;}.small .grayBox{ display: none; width: 100px; height: 100px; box-shadow: 0 0 10px rgba(0, 0, 0, 0.5); position: absolute; left: 0; top: 0;} .big{ width: 400px; height: 400px; position: absolute; left: 700px; top: 100px; border:1px solid #f10; display: none; overflow: hidden;}.big img{ position: absolute;}

function Magnifier(){}

function init(){}

function bindEvent(){}

function eleToggle(){}

function eleMove(){}

new Magnifier({ small_box : ".small", cutting_box : ".grayBox", big_box : ".big", big_img : ".big img"});

function Magnifier( options ) { // 调用初始化函数，处理接收到的参数对象 this.init( options );}

Magnifier.prototype.init = function( options ){ // 初始化元素; for(var attr in options){  this[attr+"_ele"] = this.$(options[attr]); } // 为了节省性能，所以只获取一次offsetLeft; this.small_box_offset = {  left : this.small_box_ele.offsetLeft,  top  : this.small_box_ele.offsetTop,  width : parseInt( getComputedStyle(this.small_box_ele).width ),  height : parseInt( getComputedStyle(this.small_box_ele).width ) } this.cutting_box_offset = {  width  : parseInt( getComputedStyle(this.cutting_box_ele).width ),  height : parseInt( getComputedStyle(this.cutting_box_ele).height ), } this.big_box_offset = {  width : parseInt( getComputedStyle(this.big_box_ele).width ),  height : parseInt( getComputedStyle(this.big_box_ele).height ), } // 标志变量 ，鼠标是否移入放大镜 this.magnifier_start = false; this.bindEvent(); // 图片缩放功能 this.scaleBigImg();}

Magnifier.prototype.$ = function(selector){ return document.querySelector(selector);}

Magnifier.prototype.bindEvent = function(){ // 鼠标移入左侧small_box this.small_box_ele.addEventListener( "mouseover" , function(){  // cutting_box big_box元素显示;  this.eleToggle("show");  // 修改标志变量为true  this.magnifier_start = true;  // 修改事件函数里面的this指向为当前实例对象 }.bind(this)); // 鼠标移出左侧small_box this.small_box_ele.addEventListener( "mouseout" , function(){  // cutting_box big_box元素隐藏;  this.eleToggle("hide");  this.magnifier_start = false; }.bind(this)); // 鼠标移动，元素运动; this.small_box_ele.addEventListener("mousemove" , function( evt ){  var e = evt || event;  // 获取鼠标点距离浏览器可视区的 x y 值  var x = e.clientX ;  var y = e.clientY ;  // 调用factoryPosition处理得到的坐标值  this.res = this.factoryPosition( x , y );  // 把处理好后的坐标值传入eleMove方法，改变相应的left、top值  this.eleMove( this.res ); }.bind(this));  // 滚轮事件; document.addEventListener("mousewheel" , function( evt ){  // 如果鼠标未移入放大镜，则不执行滚轮事件函数  if(!this.magnifier_start){ return false }  var e = evt || event;  // 判定滚轮向上（缩小）还是向下（放大）;  this.changeCutBoxScale( e.wheelDelta > 0 ? "narrow" : "large" ); }.bind(this));} 

Magnifier.prototype.eleToggle = function( type ){ // 根据type类型，判定元素的display的属性值 block | none this.cutting_box_ele.style.display = type === "show" ? "block" : "none"; this.big_box_ele.style.display = type === "show" ? "block" : "none";}

Magnifier.prototype.factoryPosition = function( x , y ){ // 根据接收到的 x 和 y 计算得到 cutting_box 的 left 和 top 偏移量 var _left =  x - this.small_box_offset.left - this.cutting_box_offset.width / 2; var _top  = y - this.small_box_offset.top - this.cutting_box_offset.height / 2 // cutting_box 的 left 和 top 的最大值 var _left_max = this.small_box_offset.width - this.cutting_box_offset.width; var _top_max = this.small_box_offset.height - this.cutting_box_offset.height; // 最小值边界监测; _left = _left <= 0 ? 0  : _left; _top  = _top  <= 0 ? 0  : _top // 最大值检测 _left = _left >= _left_max ? _left_max : _left; _top = _top >= _top_max ? _top_max : _top; // 返回处理好的坐标点值 以及 移动的距离与最大值的比例系数 return {  x : _left,  y : _top,  xp: _left / _left_max,  yp:_top / _top_max }}

Magnifier.prototype.eleMove =  function( position_obj ){ // 左侧cutting_box移动范围 this.cutting_box_ele.style.left = position_obj.x + "px"; this.cutting_box_ele.style.top  = position_obj.y + "px"; // 大图big_img的移动范围。cutting_box和big_img的移动方向时相反的 this.big_img_ele.style.left = -position_obj.xp * this.big_img_boundary.left_max + "px"; this.big_img_ele.style.top  = -position_obj.yp * this.big_img_boundary.top_max + "px";}

Magnifier.prototype.scaleBigImg = function(){ // 放大的比例 ; var width_p  = this.big_box_offset.width / this.cutting_box_offset.width; var height_p = this.big_box_offset.height / this.cutting_box_offset.height; // 获得了big_img放大之后的宽高; this.big_img_offset = {  width  : width_p * this.small_box_offset.width,  height : height_p * this.small_box_offset.height, } // 计算出big_img运动的边界; this.big_img_boundary = {  left_max : this.big_img_offset.width  - this.big_box_offset.width,  top_max  : this.big_img_offset.height - this.big_box_offset.height } // 给图片设置等比例宽高; this.big_img_ele.style.width  = this.big_img_offset.width + "px"; this.big_img_ele.style.height = this.big_img_offset.height + "px";}

Magnifier.prototype.changeCutBoxScale = function( type ){ switch ( type ) {  // 放大  case "large":   this.cutting_box_offset.width += 2;   this.cutting_box_offset.height += 2;   // 让cutting_box 向左 向上移动 让鼠标始终保持在中心位置    this.res.x --;   this.res.y --;    break;  // 缩小  case "narrow":   this.cutting_box_offset.width  -= 2;   this.cutting_box_offset.height -= 2;   this.res.x ++;   this.res.y ++;   break;  default:   break; } this.cutting_box_ele.style.width = this.cutting_box_offset.width + "px"; this.cutting_box_ele.style.height = this.cutting_box_offset.height + "px"; // 位置改变之后，调用相应的比例计算工具; this.scaleBigImg(); // 重新进行大图运动的计算; this.eleMove(this.res);}

<button class="btn" data-src=""><img src="" alt=""></button><button class="btn" data-src=""><img src="" alt=""></button>

// 选中所有代表不同图片的button按钮var btns = document.querySelectorAll(".btn");// 选中small 和 big 容器中的 img 标签var imgs = document.querySelectorAll(".big img,.small img");for(var i = 0 ; i < btns.length ; i ++){ btns[i].onclick = function(){  // 获取每个按钮上的不同的 data-src 属性  var src = this.getAttribute("data-src");  for(var k = 0 ; k < imgs.length ; k ++){   // 替换相应的 src 属性的属性值   imgs[k].src = src;  } }}