Common regular expressions

Exact string match

• Use the ^ and $ anchors to match the start and end of the string, respectively.
• Add the string you want to match in-between the two anchors.

const regexp = /^abc$/;
// Where 'abc' is the exact string you want to match

Match empty string

• Use the ^ and $ anchors to match the start and end of the string, respectively.
• Do not add any characters in-between to match an empty string.

const regexp = /^$/;

Match whitespace sequences

• Use the \s meta-sequence to match any whitespace character, including spaces, tabs, newlines, etc.
• Use the + quantifier to match one or more occurrences of the previous character.
• Add the global flag (g) to match all occurrences of the pattern in the string.

const regexp = /\s+/g;

Match line breaks

• Depending on the environment, line breaks can be represented in different ways.
• Use the \r character to match carriage returns, the \n character to match newlines, and the \r\n sequence to match carriage returns followed by newlines.
• Add the global (g) and multiline (m) flags to match all occurrences of the pattern in the string.

const regexp = /\r|\n|\r\n/gm;

Match non-word characters

• Use negation (^) to match any character that is not a word character (\w) or a whitespace character (\s).
• Add the global flag (g) to match all occurrences of the pattern in the string.
• Add the ignore case flag (i) to match both uppercase and lowercase characters.

const regexp = /[^\w\s]/gi;

Match alphanumeric, dashes and hyphens

• Use the ^ and $ anchors to match the start and end of the string, respectively.
• Use the a-zA-Z0-9- pattern to match any alphanumeric character, dashes and hyphens.
• Use the + quantifier to match one or more occurrences of the previous character.
• Particularly useful when matching URL slugs.

const regexp = /^[a-zA-Z0-9-_]+$/;

Match letters and whitespaces

• Use the ^ and $ anchors to match the start and end of the string, respectively.
• Use the a-zA-Z\s pattern to match any letter and whitespace character.
• Use the + quantifier to match one or more occurrences of the previous pattern.

const regexp = /^[A-Za-z\s]+$/;

Pattern not included

• Use the ^ and $ anchors to match the start and end of the string, respectively.
• Use a negative lookahead (?!) to match any character that is not followed by the pattern you want to exclude.
• Add the global flag (g) to match all occurrences of the pattern in the string.
• To ensure more than one pattern is not included, use the | character to separate them.

const regexp = /^((?!(abc|bcd)).)*$/;
// Where 'abc' and 'bcd' are pattern you want to exclude

@Further reading

Text inside brackets

• Use the \( and \) characters to match the opening and closing brackets, respectively.
• Use a capturing group between the two and exclude the closing parenthesis character.
• Use the + quantifier to match one or more characters, as needed.
• Add the global flag (g) to match all occurrences of the pattern in the string.
• Replace \( and \) with \[ and \] to match square brackets and with \{ and \} to match curly brackets.

const regexp = /\(([^)]+)\)/g;

Validate GUID/UUID

• Use the ^ and $ anchors to match the start and end of the string, respectively.
• Validate each segment of the GUID/UUID separately using numeric character ranges and quantifiers.

const regexp = /^(0?[1-9]|[12][0-9]|3[01])[\/\-](0?[1-9]|1[012])[\/\-]\d{4}$/;

Validate date format (DD/MM/YYYY)

• Use the ^ and $ anchors to match the start and end of the string, respectively.
• Validate each segment of the date separately using numeric character ranges and quantifiers.
• Alter the order of the segments and separators to match different formats.

const regexp = /^(0?[1-9]|[12][0-9]|3[01])[\/\-](0?[1-9]|1[012])[\/\-]\d{4}$/;

Chunk string into n-size chunks

• Use the .{1,n} quantifier to match any character between 1 and n times.
• Add the global flag (g) to match all occurrences of the pattern in the string.

const regexp = /.{1,2}/g;
// Where '2' is the number of characters per chunk