Use pure javascript to achieve magnifying glass effect_javascript skills

JD or Taobao’s specific products have a magnifying glass effect. Although there are many similar plug-ins on the Internet, there are many inconveniences in applying them to projects. If you take some time to write a similar plug-in yourself and accumulate code, why not do it!! let’go:

I plan to encapsulate this special effect into a plug-in. First implement the most basic algorithm, and then encapsulate it step by step:

Final effect:

html code:

Copy code The code is as follows:

css code:

Copy code The code is as follows:

It seems like there is nothing, let’s start our powerful js journey:

javascript code:

Copy code The code is as follows:

  function createElement(MagnifierId, sImg, bImg) {
            var Magnifier = $(MagnifierId);
            Magnifier.style.position = 'relative';
            //小图div
            var smallDiv = $Create("div");
            smallDiv.setAttribute("id", "small");
            smallDiv.style.position = "absolute";
            //遮罩层
            var mask = $Create("div");
            mask.setAttribute("id", "mask");
            mask.style.position = "absolute";
            //镜片
            var mirror = $Create("div");
            mirror.setAttribute("id", "mirror");
            mirror.style.opacity = 0.3;
            mirror.style.position = "absolute";
            mirror.style.display = "none";
            //小图
            var smallImg = $Create("img");
            smallImg.setAttribute("src", sImg);
            smallImg.setAttribute("id", "smallImg");
            smallImg.onload = function () {
                //如果没设置放大镜的height或者width 根据小图大小设置放大镜大小
                if (!Magnifier.offsetHeight) {
                    Magnifier.style.width = this.offsetWidth "px";
                    Magnifier.style.height = this.offsetHeight "px";
                }
                //遮罩层大小和小图一样
                mask.style.opacity = "0";
                mask.style.width = this.width 'px';
                mask.style.height = this.height "px";
                mask.style.zIndex = 2;
                bigDiv.style.left = this.width 5 "px";
                bigDiv.style.top = "-5px";
            }
            smallDiv.appendChild(mask);
            smallDiv.appendChild(mirror);
            smallDiv.appendChild(smallImg);
            //视窗
            var bigDiv = $Create("div");
            bigDiv.setAttribute("id", "big");
            bigDiv.style.position = "absolute";
            bigDiv.style.overflow = "hidden";
            bigDiv.style.display = "none";
            var bigImg = $Create("img");
            bigImg.setAttribute("src", bImg);
            bigImg.setAttribute("id", "bigImg");
            bigImg.style.position = "absolute";
            bigDiv.appendChild(bigImg);
            Magnifier.appendChild(smallDiv);
            Magnifier.appendChild(bigDiv);
        }
        function setMagnifierStyle(mirrorStyle,shichuangStyle) {
            //mirror
            for (var item in mirrorStyle) {
                mirror.style[item] = mirrorStyle[item];
            }
            for (var item in shichuangStyle) {
                $("big").style[item] = shichuangStyle[item];
            }
        }
        function registerEvent() {
            $("mask").onmouseover = function () {
                $("big").style.display = "block";
                mirror.style.display = "block";
            }
            $("mask").onmouseout = function () {
                $("big").style.display = "none";
                mirror.style.display = "none";
            }
            $("mask").onmousemove = function (evt) {
                var oEvent = evt || event;
                var disX = oEvent.offsetX;
                var disY = oEvent.offsetY;
                var mirrorLeft = disX - mirror.offsetWidth / 2;
                var mirrorTop = disY - mirror.offsetHeight / 2;
                if (mirrorLeft < 0) {
                    mirrorLeft = 0;
                }
                else if (mirrorLeft > mask.offsetWidth - mirror.offsetWidth) {
                    mirrorLeft = mask.offsetWidth - mirror.offsetWidth;
                }
                if (mirrorTop < 0) {
                    mirrorTop = 0;
                }
                else if (mirrorTop > mask.offsetHeight - mirror.offsetHeight) {
                    mirrorTop = mask.offsetHeight - mirror.offsetHeight;
                }
                mirror.style.top = mirrorTop "px";
                mirror.style.left = mirrorLeft "px";
                var paX = mirrorTop / (mask.offsetHeight - mirror.offsetHeight);
                var paY = mirrorLeft / (mask.offsetWidth - mirror.offsetWidth);
                $("bigImg").style.top = -paX * ($("bigImg").offsetHeight - $("big").offsetHeight) "px";
                $("bigImg").style.left = -paY * ($("bigImg").offsetWidth - $("big").offsetWidth) "px";
            }
        }
        function $(id) {
            return document.getElementById(id);
        }
        function $Create(type) {
            return document.createElement(type);
        }

最后再 onload小小的调用一下：

复制代码 代码如下:

 window.onload = function () {
            createElement("Magnifier", "images/Magnifier/small.jpg", "images/Magnifier/big.jpg");
            setMagnifierStyle({ "width": "30px", "height": "30px", "backgroundColor": "#fff" }, { "width": "250px", "height": "250px" });
            registerEvent();
        }

效果总算出来了耶，

2. 接下来咱们封装吧：

Magnifer类代码：

复制代码 代码如下:

function Magnifier(
Magnifierid, // magnifying the mirror container ID
sImg,                                                                                                                                                             bImg,                                                                                                                                                                                                                                     because MirrorStyle, // In the small picture lens style, json format data
                                                                                                                                                                      ) {
               var _this = this;
This.MagnifierContainer = null; //Container
This.smallDiv = null; //Small image container
This.mask = null; //Small image mask layer
            this.mirror = null;                                                                                                                                                                                                                             This.smallImg = null; //Small image
This.bigDiv = null; //Preview view
This.bigImg = null;             var init = function () {
                 _this.MagnifierContainer = _this.$(MagnifierId);
                    _this.createElement(sImg, bImg);
                  _this.setMagnifierStyle(mirrorStyle, ViewStyle);
                   _this.MainEvent();
            }
            init();
}
​ ​ Magnifier.prototype.createElement = function (sImg, bImg) {
               var _this = this;
            var $Create = this.$Create;
This.MagnifierContainer.style.position = 'relative'; //Get out of the document flow and modify it as appropriate
This.smallDiv = $Create("div");
This.smallDiv.setAttribute("id", "small");
This.smallDiv.style.position = "absolute";
This.mask = $Create("div");
This.mask.setAttribute("id", "mask");
This.mask.style.position = "absolute";
This.mirror = $Create("div");
This.mirror.setAttribute("id", "mirror");
This.mirror.style.opacity = 0.3;
This.mirror.style.position = "absolute";
This.mirror.style.display = "none";
This.smallImg = $Create("img");
This.smallImg.setAttribute("src", sImg);
This.smallImg.setAttribute("id", "smallImg");
This.smallImg.onload = function () {
//If the height or width of the magnifying glass is not set, set the size of the magnifying glass according to the size of the thumbnail
If (!_this.MagnifierContainer.offsetHeight) {
                     _this.MagnifierContainer.style.width = this.offsetWidth "px";
                      _this.MagnifierContainer.style.height = this.offsetHeight "px";
                }
//The size of the mask layer is the same as the small image
                     _this.mask.style.opacity = "0";
                    _this.mask.style.width = this.offsetWidth 'px';
                     _this.mask.style.height = this.offsetHeight "px";
                    _this.mask.style.zIndex = 2;
                     _this.bigDiv.style.left = this.offsetWidth 5 "px";
                  _this.bigDiv.style.top = "-5px";
            }
This.smallDiv.appendChild(this.mask);
This.smallDiv.appendChild(this.mirror);
This.smallDiv.appendChild(this.smallImg);
This.bigDiv = $Create("div");
This.bigDiv.setAttribute("id", "big");
This.bigDiv.style.position = "absolute";
This.bigDiv.style.overflow = "hidden";
This.bigDiv.style.display = "none";
This.bigImg = $Create("img");
This.bigImg.setAttribute("src", bImg);
This.bigImg.setAttribute("id", "bigImg");
This.bigImg.style.position = "absolute";
This.bigDiv.appendChild(this.bigImg);
This.MagnifierContainer.appendChild(this.smallDiv);
This.MagnifierContainer.appendChild(this.bigDiv);
}
        Magnifier.prototype.setMagnifierStyle = function (mirrorStyle, ViewStyle) {
            for (var item in mirrorStyle) {
                this.mirror.style[item] = mirrorStyle[item];
            }
            delete item;
            for (var item in ViewStyle) {
                this.bigDiv.style[item] = ViewStyle[item];
            }
        }
        Magnifier.prototype.MainEvent = function () {
            var _this = this;
            this.mask.onmouseover = function () {
                _this.bigDiv.style.display = "block";
                _this.mirror.style.display = "block";
            }
            this.mask.onmouseout = function () {
                _this.bigDiv.style.display = "none";
                _this.mirror.style.display = "none";
            }
            this.mask.onmousemove = function (evt) {
                var oEvent = evt || event;
                var disX = oEvent.offsetX || oEvent.layerX;  //兼容ff
                var disY = oEvent.offsetY || oEvent.layerY;
                var mirrorLeft = disX - _this.mirror.offsetWidth / 2;
                var mirrorTop = disY - _this.mirror.offsetHeight / 2;
                if (mirrorLeft < 0) {
                    mirrorLeft = 0;
                }
                else if (mirrorLeft > this.offsetWidth - _this.mirror.offsetWidth) {
                    mirrorLeft = this.offsetWidth - mirror.offsetWidth;
                }
                if (mirrorTop < 0) {
                    mirrorTop = 0;
                }
                else if (mirrorTop > this.offsetHeight - _this.mirror.offsetHeight) {
                    mirrorTop = this.offsetHeight - _this.mirror.offsetHeight;
                }
                _this.mirror.style.top = mirrorTop "px";
                _this.mirror.style.left = mirrorLeft "px";
                var paX = mirrorTop / (this.offsetHeight - _this.mirror.offsetHeight);
                var paY = mirrorLeft / (this.offsetWidth - _this.mirror.offsetWidth);
                _this.bigImg.style.top = -paX * (_this.bigImg.offsetHeight - _this.bigDiv.offsetHeight) "px";
                _this.bigImg.style.left = -paY * (_this.bigImg.offsetWidth - _this.bigDiv.offsetWidth) "px";
            }
        }
        Magnifier.prototype.$ = function (id) {
            return document.getElementById(id);
        }
        Magnifier.prototype.$Create = function (type) {
            return document.createElement(type);
        }

最后在onload调用下：

复制代码 代码如下:

window.onload = function () {
            new Magnifier(
                        "Magnifier",
                        "images/Magnifier/small.jpg",
                        "images/Magnifier/big.jpg",
                        { "width": "30px", "height": "30px", "backgroundColor": "#fff" },
                        { "width": "250px", "height": "250px" }
                );
        }

以上就是本文所述的全部内容了，希望大家能够喜欢。