JS Regular expression Validation mailbox code

The following is a regular expression that validates an e-mail message

The code is as follows	Copy Code
var re =/^w+ ([.-]?w+) *@w+ ([.-]?w+) * (. w{2,3}) +$/;

Cases

The code is as follows

Copy Code

<pre class=html name= "code" ><div> Please enter a valid mailbox: <br/> <input type= "text" size=18 id= "email" onfocus= "clearform ();"/> <input type= "button" onclick= "Validate ();" value= "Authentication"/> </div> <div id= "E-result" style= "Display:none" > The mailbox you entered is valid. Thank you! </div></PRE><BR> <script language= "JavaScript1.2" > function Vemail () { var str=document.getelementbyid (' email '). Value; if (Str.length = = 0) { Alert ("Mailbox cannot be empty"); return false; } var rule=/^ ([W-]+ (?:.) [ w-]+) @ ((?: [w-]+.) *W[W-]{0,66}). ([a-z]{2,6} (?:. [ A-z]{2})? $/i; if (Rule.test (str)) return true; else{ Alert ("Please enter a valid mailbox!"); return false; } } function Validate () { if (document.layers| | document.getelementbyid| | document.all) { if (Vemail ()) { document.getElementById (' E-result '). style.display= "Block"; } } } function ClearForm () { document.getElementById (' E-result '). style.display= "None"; document.getElementById (' email '). value= ""; } </script>

Now we're going to start dissecting this regular expression.

Re is a variable that stores the right regular expression, and in JavaScript, declares the variable to use the var keyword.

The reading order of regular expressions is Left-to-right

Regular expressions always start with (/) and end, and all content between slashes is part of a regular expression.

The caret (^) indicates that we want to use this expression to examine a string that begins with a particular string. If you remove the caret, the e-mail address may be considered valid even if there is a heap of junk characters at the beginning of the string.

An expression w represents any single character, including A~z, A~z, 0~9, or underscores. E-mail must start with these words Fu Zhi.

Plus + means we're looking for one or more occurrences of the previous entry.

The brackets () represent a group, which means that all of the contents of the parentheses are referenced later, so they are now placed in a group.

The bracket [] is used to indicate that any one of these characters can appear. In this example, the square brackets contain the characters.-. We want to allow the user to enter the dot or hyphen, but the point number is special to the regular expression, so you need to precede it with a backslash, and a backslash in front of the special character to denote the word escape, and the escaped character to represent its meaning. Because of parentheses, the input string can have a dot or a hyphen in this position, but both cannot exist at the same time.

Question mark? Indicates that the preceding entry can appear once or not. So the first part of the e-mail address can have a dot or a hyphen, or it may not.

In? Later, use w+ again to indicate that there must be other characters after the dot or hyphen.

The * number that appears after () indicates that the preceding entry can appear 0 or more times. So the contents of the parentheses can appear 0 or more times.

The @ character represents itself, without any other meaning, which is between the e-mail address and the domain name.

The @ character appears again after the w+, indicating that the character must appear after @. After that, it appears again ([.-]?w+) *, which indicates that the dot number or hyphen is allowed in the suffix of the e-mail address.

Then, create another group (. w{2,3}) in a pair of parentheses, indicating that we want to find a point number followed by some characters. In this example, the number in the curly braces indicates that the preceding entry can appear between 2 and 3 times. After this group is a + number, which means that the previous entry (this group) must appear one or more times. This will match. com or. edu, and also match ox.ac.uk.