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A regular expression is a sequence of characters that forms a pattern.
The pattern is used for searching and replacing characters in strings.
The RegExp Object is a regular expression with added Properties and Methods.
/pattern/modifier(s);
let pattern = /lynxsia/i;
/lynxsia/i is a regular expression.
lynxsia is a pattern (to be used in a search).
i is a modifier (modifies the search to be case-insensitive).
Modifiers are used to perform case-insensitive and global searches.
| Modifier | Description |
|---|---|
| g | Perform a global match (find all matches rather than stopping after the first match) |
| i | Perform case-insensitive matching |
| m | Perform multiline matching |
Brackets are used to find a range of characters.
| Expression | Description |
|---|---|
| [abc] | Find any character between the brackets |
| [^abc] | Find any character NOT between the brackets |
| [0-9] | Find any character between the brackets (any digit) |
| [^0-9] | Find any character NOT between the brackets (any non-digit) |
| (x|y) | Find any of the alternatives separated with | |
Meta characters are characters with a special meaning.
| Metacharacter | Description |
|---|---|
| . | Find a single character, except newline or line terminator |
| \w | Find a word character |
| \W | Find a non-word character |
| \d | Find a digit |
| \D | Find a non-digit character |
| \s | Find a whitespace character |
| \S | Find a non-whitespace character |
| \b | Find a match at the beginning/end of a word, beginning like this: \bHI, end like this: HI\b |
| \B | Find a match, but not at the beginning/end of a word |
| \0 | Find a NULL character |
| \n | Find a new line character |
| \f | Find a form feed character |
| \r | Find a carriage return character |
| \t | Find a tab character |
| \v | Find a vertical tab character |
| \xxx | Find the character specified by an octal number xxx |
| \xdd | Find the character specified by a hexadecimal number dd |
| \udddd | Find the Unicode character specified by a hexadecimal number dddd |
Quantifiers define quantities.
| Quantifier | Description |
|---|---|
| n+ | Matches any string that contains at least one n |
| n* | Matches any string that contains zero or more occurrences of n |
| n? | Matches any string that contains zero or one occurrences of n |
| n{X} | Matches any string that contains a sequence of X n's |
| n{X,Y} | Matches any string that contains a sequence of X to Y n's |
| n{X,} | Matches any string that contains a sequence of at least X n's |
| n$ | Matches any string with n at the end of it |
| ^n | Matches any string with n at the beginning of it |
| ?=n | Matches any string that is followed by a specific string n |
| ?!n | Matches any string that is not followed by a specific string n |
The search() method searches a string for a specified value and returns the position of the match.
let text = "Lynxsia IT Solutions";
text.search("IT"); // 8
text.search("it"); // -1
The replace() method returns a modified string where the pattern is replaced.
let text = "Lynxsia IT Solution";
text.replace("Solution","Solutions");
// OR
text.replace(/Solution/i,"Solutions");
Match a username (string) allowing only letters, numbers, and underscores.
let usernameRegex = /^\w+$/;
Match a valid email.
let emailRegex = /^\w+([.-]?\w+([.-]?\w+)*(\.\w{2,})+$/;
Match a password with at least 8 characters long and contains at least one uppercase letter, one lowercase letter, one number, and one symbol (#, ?, !, @, $, %, ^, &, *, -)
let passwordRegex = /^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[#?!@$%^&*-]).{8,20}$/;
Match a date of the format yyyy-mm-dd.
let dateRegex = /^\d{4}-\d{2}-\d{2}$/;
Match a time of the format hh:mm:ss
let timeRegex = /^([01]\d|2[0-3]):([0-5]\d):([0-5]\d)$/;
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