求大神帮忙呀

Question

 function openWindow()
{var open=confirm("确认新建窗口打开网站吗？");
if(open==true)
   {
    var url=prompt("通过输入对话框，确定打开的网址","http://www.imooc.com");
if(url!=null)
   {
window.open(url,"_blank",'width=400px,height=500px,menubar=no,toolbar=no');    
}
  else
{alert("再见！");}
}   
 else
{alert("再见！");}
    }

这个是什么意思为什么有个感叹号，为什么=null，不是=ture吗

if(url!=null)

Answer 1

！是取反的意思 即 “非”if ( url != null )  即 如果 （url 不等于 null ）{ ... }

Answer 2

JCSXRHKADKNCFFZIQPWLQGQGJNKURLYUFJISWGKGWMGQENGFFCJQZMMVLEHHNAQGXHCJTDENRIKBHQWADGDPWJMDPIOSCTTWGGCONGQKAREURKDJNRKVGPMZJNAJTENDUHPOSUBTNRORATAWDRBLFJJYIMWSFPYICLHHIZSLJWTBOGDTKXWAEYIILYLYXXQJFTNTAKUXTHQANTQDXPCIGGWWMCZMRBKVMPSFXYYYRXAQRJJJMGOLKKISIYYYQZCYOBVVEEHJMPVIEIBXRCWJJZZIFIYEBVHEQBERMFLIYRANWAENYNOYOISLFJQGZCLOKLTZZCVRLVKDJQQXIIHXHETSFQZMHGQJQRUHRBRCUVSDJWPJTXFEPPKXDNFLRCERJANGSSZWGZHRYWSCSWPGJJTJSRBUYFSBWODNTMMUCZYLSJCBLRRHJLYSVOAUEOBERCSQJYZKDUNWAWAMMZAJGUNHCRUEHKEPBEBMCLBKANSFYREYZCFVFFSRUURCATRRQKZWDXTDJSMPDDXXGKAEONXTPGOKATPPFMMLCDDTIISEVUNEOBEXRAKDKJZHEHBRKOHOXPPKNHKNQYEXXXHEKDDSWWVFWPLUNHQWTSJTYUUEUYRRSZWXDZMWWTEQPDXTDROOBBUKXOPHCBOCBKQRSHSOIEDCVSPTVTXNRGYCWZTGIDMDHAXHYATJJCMSLLIZGJWXHRKQNQGIMFSLYOSLRRRDDGRHRKNXLFRENHRAHTQFQURRLPNKAAXDMIBFOLHZTGURRXHKFSSLPISJAUBGTCQDQXAXVMSVYWDZWSPKXSGPBOERRKRBLEOIVGDZQXKNUEGMKUVVTASSVZWSIBUFVFYQJETTFSIIJSYDWKQQJTTYOLYY

Answer 3

!在js中表示非,反,不的意思.....url != null  表示判断url是不是不等于null...