Detailed explanation of regular expressions for verifying email using js (with code)

The most authentic regular statement of mailbox regex is ^[a-z0-9] ([._\\-]*[a-z0-9])*@([a-z0-9] [-a -z0-9]*[a-z0-9] .){1,63}[a-z0-9] $ Let’s explain the regular rules of

fuchangxi:

/^([a-zA-Z0-9_-])+@([a-zA-Z0-9_-])+(.[a-zA-Z0-9_-])+/

It must start with one or more word characters or -, plus @, and then one or more word characters or -. Then there is a combination of dot "." and word characters and -. There can be one or more combinations.

<script type="text/javascript"> 
function isEmail(str){ 
var reg = /^([a-zA-Z0-9_-])+@([a-zA-Z0-9_-])+(.[a-zA-Z0-9_-])+/; 
return reg.test(str); 
} 
var str = &#39;test@hotmail.com&#39;; 
document.write(isEmail(str)+&#39;<br />&#39;); 
var str2 = &#39;test@sima.vip.com&#39;; 
document.write(isEmail(str2)+&#39;<br />&#39;); 
var str3 = &#39;te-st@qq.com.cn&#39;; 
document.write(isEmail(str3)+&#39;<br />&#39;); 
var str4 = &#39;te_st@sima.vip.com&#39;; 
document.write(isEmail(str4)+&#39;<br />&#39;); 
var str5 = &#39;te.._st@sima.vip.com&#39;; 
document.write(isEmail(str5)+&#39;<br />&#39;); 
</script>

I don’t know much about the specific rules of email. I feel that this regular rule is relatively simple
Count the types of email @ prefixes

1. Pure numbers
For example: 123456@jb51.net
2. Pure letters
3. Mixed letters and numbers
4. Dotted
For example: web.blue@jb51.net
5. Underlined
For example: web_blue@jb51.net
6. With connecting lines
For example: web-blue@jb51.net
The email domain must have at least one "." and two words. To be stricter, the final top-level domain must be at least 2 letters. What is the maximum? Based on the domain name "name", the maximum is 4. If it is more relaxed, let's set it to 5^_^.
Of course the above is impossible: starting or ending with "_" or "-" and containing special symbols.
Therefore, the regular expression I gave is as follows:

^[A-Za-zd]+([-_.][A-Za-zd]+)*@([A-Za-zd]+[-.])+[A-Za-zd]{2,5}$

<script type="text/javascript"> 
fChkMail=function(szMail){ 
var szReg=/^[A-Za-zd]+([-_.][A-Za-zd]+)*@([A-Za-zd]+[-.])+[A-Za-zd]{2,5}$/; 
var bChk=szReg.test(szMail); 
return bChk; 
} 
</script> 
<input type="text" id="Mail" value="" /> 
<input type="button" value="验证邮箱地址" onclick="alert(fChkMail(document.getElementById(&#39;Mail&#39;).value));" /> 
<p>邮箱不能以 - _ .以及其它特殊字符开头和结束</p> 
<p>邮箱域名结尾为2~5个字母，比如cn、com、name</p>

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