javascript重写alert方法的实例代码

代码如下:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>重写alert</title>
    <link  href="css/style.css" rel="stylesheet"/>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.2/jquery.min.js"></script>
    <script type="text/javascript">
    var showAlert = function(msg){
        jAlert(msg, "提示！");
    }
    window.alert=showAlert;

$.alerts={
        verticalOffset:-75,horizontalOffset:0,repositionOnResize:true,overlayOpacity:.01,overlayColor:'#FFF',draggable:true,okButton:' OK ',cancelButton:' Cancel ',dialogClass:null,alert:function(message,title,callback){
            if(title==null)title='Alert';
            $.alerts._show(title,message,null,'alert',function(result){
                if(callback)callback(result)
            })
        }
        ,_show:function(title,msg,value,type,callback){
            $.alerts._hide();
            $.alerts._overlay('show');
            $("BODY").append('<div id="popup_container">'+'<h1 id="popup_title"></h1>'+'<div id="popup_content">'+'<div id="popup_message"></div>'+'</div>'+'</div>');
            if($.alerts.dialogClass)$("#popup_container").addClass($.alerts.dialogClass);
            var pos=($.browser.msie&&parseInt($.browser.version)<=6)?'absolute':'fixed';
            $("#popup_container").css({
                position:pos,zIndex:99999,padding:0,margin:0
            });
            $("#popup_title").text(title);
            $("#popup_content").addClass(type);
            $("#popup_message").text(msg);
            $("#popup_message").html($("#popup_message").text().replace(/\n/g,'<br />'));
            $("#popup_container").css({
                minWidth:$("#popup_container").outerWidth(),maxWidth:$("#popup_container").outerWidth()
            });
            $.alerts._reposition();
            $.alerts._maintainPosition(true);
            switch(type){
                case'alert':$("#popup_message").after('<div id="popup_panel"><input type="button" value="'+$.alerts.okButton+'" id="popup_ok" /></div>');
                $("#popup_ok").click(function(){
                    $.alerts._hide();
                    callback(true)
                });
                $("#popup_ok").focus().keypress(function(e){
                    if(e.keyCode==13||e.keyCode==27)$("#popup_ok").trigger('click')
                });
                break
            };
            if($.alerts.draggable){
                try{
                    $("#popup_container").draggable({
                        handle:$("#popup_title")
                    });
                    $("#popup_title").css({
                        cursor:'move'
                    })
                }
                catch(e){}
            }
        }
        ,_hide:function(){
            $("#popup_container").remove();
            $.alerts._overlay('hide');
            $.alerts._maintainPosition(false)
        }
        ,_overlay:function(status){
            switch(status){
                case'show':$.alerts._overlay('hide');
                $("BODY").append('<div id="popup_overlay"></div>');
                $("#popup_overlay").css({
                    position:'absolute',zIndex:99998,top:'0px',left:'0px',width:'100%',height:$(document).height(),background:$.alerts.overlayColor,opacity:$.alerts.overlayOpacity
                });
                break;
                case'hide':$("#popup_overlay").remove();
                break
            }
        }
        ,_reposition:function(){
            var top=(($(window).height()/ 2) - ($("#popup_container").outerHeight() /2))+$.alerts.verticalOffset;
            var left=(($(window).width()/ 2) - ($("#popup_container").outerWidth() /2))+$.alerts.horizontalOffset;
            if(top<0)top=0;
            if(left<0)left=0;
            if($.browser.msie&&parseInt($.browser.version)<=6)top=top+$(window).scrollTop();
            $("#popup_container").css({
                top:top+'px',left:left+'px'
            });
            $("#popup_overlay").height($(document).height())
        }
        ,_maintainPosition:function(status){
            if($.alerts.repositionOnResize){
                switch(status){
                    case true:$(window).bind('resize',function(){
                        $.alerts._reposition()
                    });
                    break;
                    case false:$(window).unbind('resize');
                    break
                }
            }
        }
    };
    jAlert=function(message,title,callback){
        $.alerts.alert(message,title,callback)
    }

$(function(){alert("hello word！")})
    </script>
    <style>
    #popup_container{font-family:Arial,sans-serif;font-size:12px;min-width:300px;max-width:600px;background:#FFF;border:solid 5px #999;color:#000;-moz-border-radius:5px;-webkit-border-radius:5px;border-radius:5px;}#popup_title{font-size:14px;font-weight:bold;text-align:center;line-height:1.75em;color:#666;background:#CCC url(images/title.gif) top repeat-x;border:solid 1px #FFF;border-bottom:solid 1px #999;cursor:default;padding:0em;margin:0em;}#popup_content{background:16px 16px no-repeat url(images/info.gif);padding:1em 1.75em;margin:0em;}#popup_content.alert{background-image:url(images/info.gif);}#popup_message{padding-left:48px;}#popup_panel{text-align:center;margin:1em 0em 0em 1em;}#popup_prompt{margin:.5em 0em;}
    </style>
</head>
<body>
</body>
</html>