由于系统默认alert弹出窗口不能自定义样式，有可能不符合网站的风格，虽然网上应该有很多这样的JS

但是还是自己写的比较放心，顺便练习一下对DOM的操作

支持IE6下的SELECT不能遮罩的问题，谷歌支持圆角，IE6下就比较丑了，四四方方的，不过可以自定义自己喜欢的样式

听取建议后，修改了position:fixed, IE6下用hack处理了。

点击看效果:

所需CSS：

使用方法，直接调用函数，传递所需定义的信息，支持定义是否有取消键：

alertMsg(msg, mode)

//mode为空，即只有一个确认按钮，mode为1时有确认和取消两个按钮

函数代码：添加了一个获取窗口尺寸的函数，又长长了很多，可以把获取窗口的尺寸另外立一个函数放公共库里面，这里只是为了方便演示，写到一个函数里面

function alertMsg(msg, mode) { //mode为空，即只有一个确认按钮，mode为1时有确认和取消两个按钮

msg = msg || '';

mode = mode || 0;

var top = document.body.scrollTop || document.documentElement.scrollTop;

var isIe = (document.all) ? true : false;

var isIE6 = isIe && !window.XMLHttpRequest;

var sTop = document.documentElement.scrollTop || document.body.scrollTop;

var sLeft = document.documentElement.scrollLeft || document.body.scrollLeft;

var winSize = function(){

var xScroll, yScroll, windowWidth, windowHeight, pageWidth, pageHeight;

// innerHeight获取的是可视窗口的高度，IE不支持此属性

if (window.innerHeight && window.scrollMaxY) {

xScroll = document.body.scrollWidth;

yScroll = window.innerHeight + window.scrollMaxY;

} else if (document.body.scrollHeight > document.body.offsetHeight) { // all but Explorer Mac

xScroll = document.body.scrollWidth;

yScroll = document.body.scrollHeight;

} else { // Explorer Mac...would also work in Explorer 6 Strict, Mozilla and Safari

xScroll = document.body.offsetWidth;

yScroll = document.body.offsetHeight;

}

if (self.innerHeight) { // all except Explorer

windowWidth = self.innerWidth;

windowHeight = self.innerHeight;

} else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode

windowWidth = document.documentElement.clientWidth;

windowHeight = document.documentElement.clientHeight;

} else if (document.body) { // other Explorers

windowWidth = document.body.clientWidth;

windowHeight = document.body.clientHeight;

}

// for small pages with total height less then height of the viewport

if (yScroll < windowHeight) {

pageHeight = windowHeight;

} else {

pageHeight = yScroll;

}

// for small pages with total width less then width of the viewport

if (xScroll < windowWidth) {

pageWidth = windowWidth;

} else {

pageWidth = xScroll;

}

return{

'pageWidth':pageWidth,

'pageHeight':pageHeight,

'windowWidth':windowWidth,

'windowHeight':windowHeight

}

}();

//alert(winSize.pageWidth);

//遮罩层

var styleStr = 'top:0;left:0;position:absolute;z-index:10000;background:#666;width:' + winSize.pageWidth + 'px;height:' + (winSize.pageHeight + 30) + 'px;';

styleStr += (isIe) ? "filter:alpha(opacity=80);" : "opacity:0.8;"; //遮罩层DIV

var shadowDiv = document.createElement('div'); //添加阴影DIV

shadowDiv.style.cssText = styleStr; //添加样式

shadowDiv.id = "shadowDiv";

//如果是IE6则创建IFRAME遮罩SELECT

if (isIE6) {

var maskIframe = document.createElement('iframe');

maskIframe.style.cssText = 'width:' + winSize.pageWidth + 'px;height:' + (winSize.pageHeight + 30) + 'px;position:absolute;visibility:inherit;z-index:-1;filter:alpha(opacity=0);';

maskIframe.frameborder = 0;

maskIframe.src = "about:blank";

shadowDiv.appendChild(maskIframe);

}

document.body.insertBefore(shadowDiv, document.body.firstChild); //遮罩层加入文档

//弹出框

var styleStr1 = 'display:block;position:fixed;_position:absolute;left:' + (winSize.windowWidth / 2 - 200) + 'px;top:' + (winSize.windowHeight / 2 - 150) + 'px;_top:' + (winSize.windowHeight / 2 + top - 150)+ 'px;'; //弹出框的位置

var alertBox = document.createElement('div');

alertBox.id = 'alertMsg';

alertBox.style.cssText = styleStr1;

//创建弹出框里面的内容P标签

var alertMsg_info = document.createElement('P');

alertMsg_info.id = 'alertMsg_info';

alertMsg_info.innerHTML = msg;

alertBox.appendChild(alertMsg_info);

//创建按钮

var btn1 = document.createElement('a');

btn1.id = 'alertMsg_btn1';

btn1.href = 'javas' + 'cript:void(0)';

btn1.innerHTML = '确定';

btn1.onclick = function () {

document.body.removeChild(alertBox);

document.body.removeChild(shadowDiv);

return true;

};

alertBox.appendChild(btn1);

if (mode === 1) {

var btn2 = document.createElement('a');

btn2.id = 'alertMsg_btn2';

btn2.href = 'javas' + 'cript:void(0)';

btn2.innerHTML = '取消';

btn2.onclick = function () {

document.body.removeChild(alertBox);

document.body.removeChild(shadowDiv);

return false;

};

alertBox.appendChild(btn2);

}

document.body.appendChild(alertBox);

}