Regular Expression example

Regular Expression matching Chinese characters: [/u4e00-/u9fa5]

Match double-byte characters (including Chinese characters): [^/x00-/xFF]

Application: Calculate the length of a string (two-byte length Meter 2, ASCII character meter 1)

String. Prototype. Len = function () {return this. Replace ([^/x00-/xFF]/g, "AA"). length ;}

Regular Expression for matching empty rows:/n [/S |] */R

Regular Expressions matching HTML tags:/<(. *)>. * </1> | <(. *)/>/

Regular Expression matching spaces at the beginning and end: (^/S *) | (/S * $)

Match the regular expression of the email address:/W + ([-+.] /W +) * @/W + ([-.] /W + )*/. /W + ([-.] /W + )*

The regular expression matching the URL: http: // ([/W-] +/.) + [/W-] + (/[/W -./? % & =] *)?

/(/D +)/. (/d +)/g // match the regular expression of the IP address

The following describes how to use a regular expression to match an IP address and convert the IP address to a corresponding value in Javascript.Program:

Function ip2v (IP)
{
Re =/(/d +)/. (/d +)/g // The regular expression that matches the IP address
If (Re. Test (IP ))
{
Return Regexp. $1 * Math. Pow (255) + Regexp. $2 * Math. Pow () + Regexp. $3 * + Regexp. $4*1
}
Else
{
Throw new error ("not a valid IP address! ")
}
}

Use regular expressions to restrict text box input in a webpage form:

You can only enter Chinese characters using regular expressions: onkeyup = "value = value. replace (/[^/u4e00-/u9fa5]/g, '')" onbeforepaste = "clipboardData. setdata ('text', clipboardData. getdata ('text '). replace (/[^/u4e00-/u9fa5]/g ,''))"

You can only enter the full-width characters: onkeyup = "value = value. replace (/[^/uff00-/Uffff]/g, '')" onbeforepaste = "clipboardData. setdata ('text', clipboardData. getdata ('text '). replace (/[^/uff00-/Uffff]/g ,''))"

Use a regular expression to limit that only numbers can be entered: onkeyup = "value = value. replace (/[^/d]/g, '')" onbeforepaste = "clipboardData. setdata ('text', clipboardData. getdata ('text '). replace (/[^/d]/g ,''))"

You can only enter numbers and English letters using regular expressions: onkeyup = "value = value. replace (/[/W]/g, '')" onbeforepaste = "clipboardData. setdata ('text', clipboardData. getdata ('text '). replace (/[^/d]/g ,''))"

^/D + $ // match a non-negative integer (positive integer + 0)
^ [0-9] * [1-9] [0-9] * $ // match a positive integer
^ (-/D +) | (0 +) $ // match a non-positive integer (negative integer + 0)
^-[0-9] * [1-9] [0-9] * $ // match a negative integer
^ -? /D + $ // match the integer
^/D + (/./d + )? $ // Match non-negative floating point number (Positive floating point number + 0)
^ ([0-9] + /. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] */. [0-9] +) | ([0-9] * [1-9] [0-9] *) $ // matches the Positive floating point number
^ (-/D + (/./d + )?) | (0 + (/. 0 + )?)) $ // Match a non-Positive floating point number (negative floating point number + 0)
^ (-([0-9] + /. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] */. [0-9] +) | ([0-9] * [1-9] [0-9] *) $ // matches a negative floating point number.
^ (-? /D +) (/./d + )? $ // Match floating point numbers
^ [A-Za-Z] + $ // match a string consisting of 26 English letters
^ [A-Z] + $ // match a string consisting of 26 uppercase letters
^ [A-Z] + $ // match a string consisting of 26 lowercase letters
^ [A-Za-z0-9] + $ // match a string consisting of digits and 26 letters
^/W + $ // match a string consisting of digits, 26 English letters, or underscores
^ [/W-] + (/. [/W-] +) * @ [/W-] + (/. [/W-] +) + $ // match the email address
^ [A-Za-Z] +: // match (/W + (-/W + )*)(/. (/W + (-/W + )*))*(/? /S *)? $ // Match the URL