Java Script

Pattern Matching Using Regular Expressions

Metacharacters

• Character class– [abc] matches ‘a’ or ‘b’ or ‘c’– [a-z] matches a through z– [^aeiou] matches any character except a vowel

• ^ - beginning of the string• $ - end of the string

Predefined Character ClassesName Equivalent Pattern Matches

\d [0-9] A digit

\D [^0-9] Not a digit

\w [A-Za-z_0-9] A word character (alphanumeric)

\W [^A-Za-z_0-9] Not a word character

\s [ \r\t\n\f] A whitespace character

\S [^ \r\t\n\f] Not a whitespace character

Matches

var matches = str.match(/^\d\.\d\d$/);matches 3.14

var matches = str.match(/^\w\w\w$/);var matches = str.match(/^\w{3}$/);

matches abc or 123 or Abc

* + Metacharacters

• * = zero or more• + = one or morevar matches = str.match(/^\d+\.\d*$/);

matches 123.45 or 123.

var matches = str.match(/^[A-Za-z]\w*$/);identifiers in programming languages

Social Security Number

if(!document.forms[0].mySSN.value.match(/^\d{3}-\d{2}-\d{4}$/);

{alert(“Invalid ssn.”); return false;}

^ = beginning of string$ = end of string

? Metacharacter

Parse Zip Code

var zipcode = str.match(/^\d{5}(-\d{4})?$/);

date

If(str.match(/^1?\d\/\d?\d\/\d\d$/) == null){

alert(“invalid date”);}

? = zero or one

Trim

• date = date.trim();