今天看啥 热点：
js中各种类型的变量在if条件中是true还是false，jsfalse
js的弱类型让人感觉很多东西都比较迷惑，例如变量在if条件中到底是true还是false，如果在强类型语言中将一个非boolean类型的变量放在if条件中时，是需要进行类型转换的，但是js不需要，下面来进行测试，测试常见的变量类型在if条件中的表现
!function test1(){
&span style="color:#ff0000;"&var a,b=-1,c= 1,d= 0,e=null,f=undefined,g='',h="";&/span&
console.log('a='+a)
console.log("b="+b)
console.log("c="+c)
console.log("d="+d)
console.log("e="+e)
console.log("f="+f)
console.log("g="+g)
console.log("h="+h)
设定了各种变量类型，分别放入if条件中
a=undefined
f=undefined
if(){语句}当括号里面的值为0
空字符 false
undefined 的时候就相当于false
则不执行语句
除此之外的值就执行语句
//定义一个变量没有初始化if(a){alert(1) return};//这里不会执行，因为a没有值，所以为false；a=0//这里给a赋值为0if(a){alert(1) return};//在来执行这句话，因为a=0；0代表false，所以还是不执行；a=1或者a=“123”；if(a){alert(1) return};//这里a=除0以为的数，或者字符或者obj都表示为真，这里的alert就会执行！ 在来看第二种情况；if(b==&&)和if(b==null)这里谁会执行呢，当然是后面一种，因为b是没有定义值的，如果是var b=&&，这样的话就会执行第一种;b = 1;if(b==1)和if(b==&1&)这里哪一种会执行呢，答案是两种都会执行！因为js的==表示的是数值相等；谢谢，希望楼主可以理解！ 还有就是楼主的这种情况：c=0;if(c==false)会不会执行呢，答案是肯定的；c=1;if(c==true)也一样会执行！但是我们看下面这样会执行么？c=2或者c=&admin&if(c==true)alert(1)这句话会执行么，答案是否定的，因为默认表示的是，0为false而1为true，对于其他的就没有这么定义，所以这里不会执行，当然如果你是这样if(c)那这里就会执行了！
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HTML/Xhtml最近更新I can answer the question you asked.If I were an inventor,I would invent a machine which can take the time back by operating.And only the honest and virtuous man can operate it.If it could be ture,people would be able to redo the events which they did not do so good as they supposed and people would have no sorry thing 的翻译是：I can answer the question you asked. If I were an inventor,I would invent a machine which can take the time back by operating. And only the honest and virtuous man can operate it. If it could be ture,people would be able to redo the events which they did not do so good as they supposed and people wo 中文翻译英文意思，翻译英语
请在下面的文本框内输入文字，然后点击开始翻译按钮进行翻译，如果您看不到结果，请重新翻译！
I can answer the question you asked.If I were an inventor,I would invent a machine which can take the time back by operating.And only the honest and virtuous man can operate it.If it could be ture,people would be able to redo the events which they did not do so good as they supposed and people would have no sorry thing
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I can answer the question you asked.If I were an inventor, I would invent a machine which can take the time back by operating.And only the honest and virtuous man can operate it.If it could be ture, people would be able to redo the events which they did not do so good as they supposed and people wou
I can answer the question you asked. If I were an inventor,I would invent a machine which can take the time back by operating. And only the honest and virtuous man can operate it. If it could be ture,people would be able to redo the events which they did not do so good as they supposed and people wo
I can answer the question you asked. If I were an inventor,I would invent a machine which can take the time back by operating. And only the honest and virtuous man can operate it. If it could be ture,people would be able to redo the events which they did not do so good as they supposed and people wo
I can answer the question you asked. If I were an inventor, I would invent a machine which can take the time back by operating. And only the honest and virtuous man can operate it. If it could be ture, people would be able to redo the events which they did not do so good as they supposed and people
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& alow pile 低堆 & aKarina and her lucky boyfriend enjoy having sex on a sultry summer afternoon – while you watch! Dylan was sitting by the pool checking his email when Karina walked up wearing a summer dress. She wanted his attention, which didn’t take long. -，当您观看时， Karina和她的幸运男朋友在一个闷热夏天下午喜欢有性! 当Karina走了穿夏天礼服，由水池坐检查他的电子邮件的Dylan。 她想要他的注意，很多时间没有花费。 & aSusan摇头 苏珊摇头 & aVMware Workstation and Hyper-V are not compatible.
You must remove the Hyper-V role from your system before running VMware Workstation 正在翻译，请等待...
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&!DOCTYPE&&html&&head&&meta http-equiv="Content-Type" content="text.charset=utf-8"&&title&复习一下confirm属性&/title&&script& var addf=confirm("您好 想要进入该网站吗"); if(true){
document.write("欢迎访问本网站 很高兴为你服务");
alert("谢谢 忍痛拒绝"); } &/script& &/head& &body& &/body& &/html&
非常感谢！
请问在if后面写addf和addf=true还有addf==true有什么区别吗?
addf = true 是赋值语句并不是判断语句，这条语句的意思是把addf的值定为true，而addf == true 和直接写addf是一样的，都是判断addf是否是true
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为什么if（true）然后不能正常输出结果呢 然后if（addf）又可以输出结果了 好懵
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完全没接触过代码吗。。。简单通俗的说就是if(条件) 条件有个值true或者false，这个addf变量的值由confirm确定，点确定addf=true,点取消addf=false。
你得去了解下其他的编程语言再看这个
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