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Use pure javascript to achieve magnifying glass effect_javascript skills

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May 16, 2016 pm 04:08 PM

javascriptmagnifier

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 
                    mirrorLeft = 0;

                }

                else if (mirrorLeft > mask.offsetWidth - mirror.offsetWidth) {

                    mirrorLeft = mask.offsetWidth - mirror.offsetWidth;

                }

                if (mirrorTop 
                    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 
                    mirrorLeft = 0;

                }

                else if (mirrorLeft > this.offsetWidth - _this.mirror.offsetWidth) {

                    mirrorLeft = this.offsetWidth - mirror.offsetWidth;

                }

                if (mirrorTop 
                    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。

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