@foxxmd/regex-buddy-core

Javascript helper functions for handling Regular Expressions and parsing user input as Regular Expressions

Docs best viewed at foxxmd.github.io/regex-buddy-core

Why?

Normalize All The Things

Are you tired of dealing with different results based on whether a Regex is global or not? Do you hate having to deal with match, test, matchAll, and exec?

Use regex-buddy's parseRegex with any Regex object and get back:

• On no match => undefined
• On 1 or more matches (regardless of global) => an array of RegExResult objects that contain all the context you need.

Expressionize All The Strings

Do you want to allow users to search/match strings? What about allowing users to search/match a string with Regular Expressions? But isn't that a headache??

Not anymore! With regex-buddy's parseToRegex and parseToRegexOrLiteralSearch, using the power of @stdlib/regexp-regexp under the hood, you can treat any search input as a regular expression and gracefully fallback to "dumb" searching. Always get a RegExp object back regardless of the input given!

Install

npm install @foxxmd/regex-buddy-core

Usage

Functions

parseToRegex()

Uses @stdlib/regexp-regexp to convert a regular string into a Regular Expression RegExp object.

Args

• val: string - Value to convert EX '/^my (reg)ular expression$/'
• defaultFlags?: string - Optional flags to add to the parsed expression, if none were found.

Example

import {parseToRegex} from '@foxxmd/regex-buddy-core';

const myReg = parseToRegex('/my (reg)?ular expression/', 'i');
myReg.test('this string has my ReGuLaR expression in it'); // true

const myPlainStr = parseToRegex('just some plain string');
console.log(myPlainStr); //undefined

parseToRegexOrLiteralSearch()

Tries to convert a regular string into a RegExp object using parseToRegex(). If the string is not a valid regular expression then the string is escaped and used as character literals to create a "dumb" expression that matches the string's value as-is. If the string cannot be converted to a valid expression an error is thrown.

Args

• val: string - Value to convert EX '/^my (reg)ular expression$/'
• options? - Can be either
  • An optional string of flags to add to the parsed expression, if none were found.
  • A LiteralSearchOptions object used to customize the literal search expression generated.

Example

import {parseToRegexOrLiteralSearch} from '@foxxmd/regex-buddy-core';

const strAsReg = parseToRegexOrLiteralSearch('/my (reg)?ular expression/', 'i');
strAsReg.test('this string has my ReGuLaR expression in it'); // true

const plainStr = parseToRegexOrLiteralSearch('exactStr', 'i'); // defaults to behavior: 'exact'
strAsReg.test('exactSTR'); // true

const containsStr = parseToRegexOrLiteralSearch('anywhere', {flags: 'i', behavior: 'contains'});
containsStr.test('has the keyword anywhere in the string'); // true

parseToRegexOrLiteralSearchCached()

A wrapped version of parseToRegexOrLiteralSearch that caches RegExp based on unique inputs of val, options.behavior, and default flags.

Provide either a max number of cached entries or provide your own implementation of SimpleCache.

parseRegex()

Takes a RegExp and string value to test and returns:

• If no matches => undefined
• If any matches => An array of RegExResult

parseRegex will handle the expression regardless of whether it is global or not. If it is global then the returned array will contain all matches. If it is not global the returned array will only have one result.

Args

• reg: RegExp - Regular Expression object to test with
• val: string - The string to test on

Example

import {parseRegex} from '@foxxmd/regex-buddy-core';

const normalRes = parseRegex(new RegExp(/my (reg)?ular (?<myGroup>exp)ression/i), 'this string has my ReGuLaR expression in it');
console.log(normalRes); // [ {...} ]
console.log(normalRes[0]);
// {
//     match: 'this string has my ReGuLaR expression in it',
//     index: 0,
//     groups: ['reg'],
//     named: {
//         myGroup: 'exp'
//     }
// }

const noRes = parseRegex(new RegExp(/my (reg)?ular (?<myGroup>exp)ression/i), 'it has no match');
console.log(noRes); // undefined

const globalRes = parseRegex(new RegExp(/all matches/g), 'this has all matches because it globally has all matches');
console.log(globalRes);
// [
//     {
//         match: 'this has all matches because it globally has all matches',
//         index: 9,
//         groups: [],
//         named: {}
//     },
//     {
//         match: 'this has all matches because it globally has all matches',
//         index: 45,
//         groups: [],
//         named: {}
//     }
// ]

parseRegexSingle()

A convenience function for dealing with non-global expressions. The same as parseRegex() except:

• throw an error if more than one match (does not allow global)
• return result is either undefined or RegexResult (not an array)

Example

import {parseRegexSingle} from '@foxxmd/regex-buddy-core';

const normalRes = parseRegexSingle(new RegExp(/my (reg)?ular (?<myGroup>exp)ression/i), 'this string has my ReGuLaR expression in it');
console.log(normalRes);
// {
//     match: 'this string has my ReGuLaR expression in it',
//     index: 0,
//     groups: ['reg'],
//     named: {
//         myGroup: 'exp'
//     }
// }

const noRes = parseRegexSingle(new RegExp(/my (reg)?ular (?<myGroup>exp)ression/i), 'it has no match');
console.log(noRes); // undefined

const globalRes = parseRegexSingle(new RegExp(/all matches/g), 'this has all matches because it globally has all matches'); // THROWS AN ERROR

testMaybeRegex()

A convenience function that parses a string using parseToRegexOrLiteralSearch(), tests it against a value, and returns a tuple of:

• boolean Whether a match was found
• string The (first) matched string

Args

• test: string - Value to convert to an expression
• subject: string - The string to test on
• options? - Can be either
  • An optional string of flags to add to the parsed expression, if none were found.
  • A LiteralSearchOptions object used to customize the literal search expression generated.
    • If behavior is not defined then contains is used.

Example

import {testMaybeRegex} from '@foxxmd/regex-buddy-core';

const result = testMaybeRegex('/my (reg)?ular expression/', 'this string has my ReGuLaR expression in it');
console.log(result); // [true, 'my ReGuLaR expression']

const noMatch = testMaybeRegex(new RegExp(/my (reg)?ular (?<myGroup>exp)ression/i), 'it has no match');
console.log(noMatch); // undefined

searchAndReplace()

Perform one or more search-and-replace functions on a string by providing SearchAndReplaceRegExp criteria. This is very similar to String.replace() except that:

• it can accept multiple search-and-replace operations that are performed on the resulting value of each previous operation
• the search value can be a RegExp object, or a string that that is converted using parseToRegexOrLiteralSearch())

Args

• val?: string - String to perform operations on
• ops: SearchAndReplaceRegExp[] - One or more search-and-replace criteria to use for the operations.
• options? - Optional, how to convert search string values to literal searches. Can be either
  • An optional string of flags to add to the parsed expression, if none were found.
  • A LiteralSearchOptions object used to customize the literal search expression generated.
    • If behavior is not defined then contains is used.

Example

import {searchAndReplace} from '@foxxmd/regex-buddy-core';

const ops = [
  {
      search: '/remove (this)/',
      replace: ''
  },
  {
      search: '/TEST/ig',
      replace: 'DOUBLETEST'
  }
];

const result = searchAndReplace('this is a TeSt which will remove this TEST', ops);
console.log(result); // this is a DOUBLETEST which will remove DOUBLETEST

Interfaces

LiteralSearchOptions

An object that defines how a string is handled prior to usage as a literal string expression as well as how to search for the literal string.

• flags?: string - Optional flags to add to the parsed literal search expression
• trim?: boolean - Trim whitespace from string value before transforming and escaping
• transform?: (SearchAndReplaceRegExp | SearchAndReplaceRegExp[]) - One or more search-and-replace criteria used to transform the string value before using it as the literal search expression
• escapeTransform?: SearchAndReplaceRegExp - A search-and-replace criteria used to escape the string value before it is inserted into the literal search expression. This operation is run after any transform operations. A default escape function is provided.
• behavior?: string - How the literal search value expression should be built IE how to search for the value in a string:
  • exact => tested string must match the search value exactly
  • contains => search value must be present somewhere within the tested string
  • startsWith => search value must be present at the beginning of the tested string
  • endsWith => search value must be present at the end of the tested string

SearchAndReplaceRegExp

Criteria used to perform a search-and-replace operation on a string. This is very similar to String.replace() except that string value used for search will be converted to RegExp first using parseToRegexOrLiteralSearch().

• search: (string | RegExp) - The search value to test for. Can be a normal string (converted to a case-sensitive literal) or a valid regular expression as a string, or an actual RegExp object.
• replace: string - The replacement string/value to use when search is found. This can be a literal string like 'replace with this', an empty string to remove the search value (''), or a special regex value.

RegExResult

A normalized regular expression match.

• match: string - The subset of the string that matched the expression
• index: number - The zero-based index of the string where the matched expression began
• groups: (string|undefined)[] - An array of values from capture groups in the expression. If a capture group did not match its value is undefined.
• named: { [string]: string } - An object with (key => values) consisting of (named capture group name => capture group value)

License

MIT