要想实现弹窗的效果，首先应该创建一个覆盖层maskLayer，以及一个显示层presentLayer。
其次，每次弹窗时（除首次弹窗外），maskLayer的显示以及隐藏不应该导致文档流的reflow，但是repaint不可避免。所以对于maskLayer，用以display:absolute;
最为关键的就是显示层的定位居中显示，根据maskLayer的高度和宽度计算出显示层的位置。
另外，为了多样性的支持弹窗的内容，该实现也提供了ajax抓取的相应功能，但具体并未测试，仓促做出的简单测试也并不完美。
为了节约空间大小，直接将该页面呈现。
<!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"> <title></title> <style> html,body{margin: 0;padding: 0;overflow: hidden;} #maskLayer{position: absolute;z-index: 1000;} #presentLayer{position: absolute;z-index: 1500;border: 10px solid #e3e3e3;background: url(img/preload.gif) center center no-repeat;} </style> </head> <body> <img id="test" src="http://image.zhangxinxu.com/image/study/s/mm10.jpg" width="200" height="200"> <script> document.querySelector('#test').addEventListener('click',function(){ var img = '<img src="http://image.zhangxinxu.com/image/study/s/mm10.jpg" width="640" height="466">' var clk = "<object classid='clsid:D27CDB6E-AE6D-11cf-96B8-444553540000' width='550' height='400'><param name='movie' value='img/as3_clock_2.swf' /><param name='quality' value='high' /><param name='wmode' value='opaque' /><embed height='400' width='550' src='img/as3_clock_2.swf' type='application/x-shockwave-flash'></embed></object>"; var con = '3s后即将关闭'; Popup.u.show(clk,0,0,0,1); },false) </script> <script> (function(window){ function get(id){ return document.getElementById(id); } if(!window.Popup) var Popup = {}; window.Popup = Popup; Popup.u = function(){ var maskLayer,presentLayer,contentLayer, scontent,sisAjax,swidth,sheight,sauto; var f = false return { /** * @param content * @param isAjax * @param width * @param height * @param auto 自适应宽度高度 * @param timeout */ show: function(content,isAjax,width,height,auto,timeout){ var that = this; if(!maskLayer){ maskLayer = document.createElement('div'); maskLayer.id = 'maskLayer' presentLayer = document.createElement('div'); presentLayer.id = 'presentLayer'; presentLayer.style.position = 'absolute'; contentLayer = document.createElement('div'); contentLayer.id = 'contentLayer'; contentLayer.style.display = 'none'; maskLayer.style.position = 'absolute'; maskLayer.style.top = 0; document.body.appendChild(maskLayer); document.body.appendChild(presentLayer); presentLayer.appendChild(contentLayer); maskLayer.onclick = this.hide; window.onresize = this.resize; } scontent = content; sisAjax = isAjax; swidth = width; sheight = height; sauto = auto; this.spread(); this.preshow(); this.filter(maskLayer,80,3,1); if (timeout) setTimeout(that.hide,timeout * 1000); }, load: function(content,isAjax,width,height,auto){ var that = this; if(isAjax){ var xhr = that.ajax(); xhr.onreadystatechange = function(){ if(xhr.readyState == 4){ if(xhr.status >= 200 && xhr.status < 300 || xhr.status == 304){ that.process(xhr.responseText,width,height,auto); } } }; xhr.open('GET',content,true); xhr.send(null); }else{ that.process(content,width,height,auto); } }, hide: function(){ Popup.u.filter(presentLayer,0,5,-1); }, process: function(content,width,height,auto){ if(auto){ if(!width && !height){ var preW = parseInt(presentLayer.style.width), preH = parseInt(presentLayer.style.height); presentLayer.style.width = ''; presentLayer.style.height = ''; contentLayer.style.width = ''; contentLayer.style.height = ''; contentLayer.style.display = ''; presentLayer.style.backgroundImage = 'none'; contentLayer.innerHTML = content; }else{ presentLayer.style.width = width; presentLayer.style.height = height; } this.layout(preW,preH,width,height); } }, ajax: function(){ var that = this,fns; fns = [function(){return new window.XMLHttpRequest();},function(){return new ActiveXObject('Msxml2.XMLHTTP')}, function(){return new ActiveXObject('Microsoft.XMLHTTP')}]; for(var i,len = fns.length;i<len;i++){ try{ new fns[i](); that.ajax = fns[i]; break; }catch (e){} } return ajax(); }, resize: function(){ Popup.u.position(); Popup.u.spread(); }, // presentLayer 初始显示 preshow: function(bgimg){ var clientHeight = Popup.p.clientHeight(),clientWidth = Popup.p.clientWidth(), setTop,setLeft; bgimg = bgimg?bgimg:''; presentLayer.style.display = 'none'; presentLayer.style.backgroundColor = '#fff'; presentLayer.style.backgroundImage = bgimg; presentLayer.style.width = '100px'; presentLayer.style.height = '100px'; setTop = (clientHeight - 100) / 2; setLeft = (clientWidth - 100) /2; setTop = setTop < 20 ? 20 : setTop; presentLayer.style.left = setLeft + 'px'; presentLayer.style.top = setTop + 'px'; presentLayer.style.display = ''; return; }, /** * @param bgimg * 遮盖层展开，设置height width **/ spread: function(bgimg){ bgimg = bgimg?bgimg:''; maskLayer.style.backgroundColor = '#303030'; maskLayer.style.backgroundImage = bgimg; maskLayer.style.width = Popup.p.pageWidth() + 'px'; maskLayer.style.height = Popup.p.pageHeight() + 'px'; return; }, // 定位 presentLayer position: function(){ var clientHeight = Popup.p.clientHeight(), clientWidth = Popup.p.clientWidth(), boxW,boxH,setLeft,setTop; boxH = presentLayer.offsetHeight; boxW = presentLayer.offsetWidth; setTop = Math.abs(clientHeight - boxH) / 2; console.log(setTop) setLeft = Math.abs(clientWidth - boxW) /2; setTop = setTop < 20 ? 20 : setTop; presentLayer.style.left = setLeft + 'px'; presentLayer.style.top = setTop + 'px'; return ; }, layout: function(preW,preH,width,height){ // 设定presentLayer 和 contentLayer的位置关系 var padding,margin, finW,finH, that = this, factorW,factorH, curW = preW,curH = preH, timeid; /*console.log('presentLayer:'+presentLayer.offsetWidth+" "+presentLayer.offsetHeight) console.log('contentLayer:'+contentLayer.offsetWidth+" "+contentLayer.offsetHeight) */ if(!width && !height){ finW = contentLayer.offsetWidth; finH = contentLayer.offsetHeight; }else{ finW = width; finH = height; } factorW = finW > preW ? 1 : -1; factorH = finH > preH ? 1 : -1; presentLayer.style.paddingBottom = '10px'; presentLayer.style.paddingTop = '10px'; presentLayer.style.paddingLeft = '10px'; presentLayer.style.paddingRight = '10px'; contentLayer.style.display = ''; function recurse(){ if(curW == finW){ if(curH == finH){ clearInterval(timeid); that.position(); contentLayer.style.display = ''; return; } }else{ curW += Math.ceil(Math.abs(finW - curW) / 3) * factorW; presentLayer.style.width = curW + 'px'; } if(curH == finH){ if(curW == finW){ clearInterval(timeid); that.position(); contentLayer.style.display = ''; return; } }else{ curH += Math.ceil(Math.abs(finH - curH) / 3) * factorH; presentLayer.style.height = curH + 'px'; } that.position(); } timeid = setInterval(recurse,20); }, /** * @param el * @param opacity * @param factor 每次迭代所增减的因子 * @param iod 增减性，取值为正负1. -1 则意味着透明度逐渐为零 */ filter: function(el,opacity,factor,iod){ if(el.uuid){ clearInterval(el.uuid); } var curVal = 0,that = this; if(iod == -1){ curVal = el.style.opacity * 100; }else{ el.style.opacity = 0; el.style.filter = 'alpha(opacity=0)'; } function recurse(){ if(curVal == opacity){ clearInterval(el.uuid); el.uuid = null; if(iod == 1){ // 先显示maskLayer，然后显示presentLayer el.style.display = ''; el === maskLayer ? that.filter(presentLayer,100,5,1) : that.load(scontent,sisAjax,swidth,sheight,sauto); }else{ // 先隐藏presentLayer el.style.display = 'none'; if(el === presentLayer){ el.style.width = el.style.height = 0; } el === presentLayer ? that.filter(maskLayer,0,3,-1):contentLayer.innerHTML = ''; } }else{ curVal += Math.ceil(Math.abs(opacity - curVal) / factor) * iod; el.style.opacity = curVal / 100; el.style.filter = 'alpha(opacity=' + curVal + ')'; } } el.uuid = setInterval(recurse,20); } }; }(); Popup.p = function(){ var h = document.documentElement,b = document.body; return { pageWidth: function(){return Math.max(Math.max(h.scrollWidth, b.scrollWidth),Math.max(h.offsetWidth, b.offsetWidth))}, pageHeight: function(){return Math.max(Math.max(h.scrollHeight, b.scrollHeight),Math.max(h.offsetHeight, b.offsetHeight))}, clientWidth: function(){return window.innerWidth || h.clientWidth || b.clientWidth}, clientHeight: function(){return window.innerHeight || h.clientHeight || b.clientHeight} } }(); })(window); </script> </body> </html>