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regexResultArrayGroups

Reports indexed access on regex result arrays when named capturing groups should be used.

✅ This rule is included in the ts stylisticStrict presets.

When a regular expression has named capturing groups, accessing the matched values through .groups.name is more readable and maintainable than using numeric indices like result[1]. Numeric indices are fragile because they can break if the regex pattern is modified (e.g., adding a new capturing group before the one you’re accessing).

This rule reports indexed access on regex result arrays when the index corresponds to a named capturing group.

Examples

Section titled “Examples”

RegExp.prototype.exec()

Section titled “RegExp.prototype.exec()”
const 
const regex: RegExp
regex = /a(?<foo>b)c/;
const 
const match: RegExpExecArray | null
match = 
const regex: RegExp
regex.
RegExp.exec(string: string): RegExpExecArray | null
Executes a search on a string using a regular expression pattern, and returns an array containing the results of that search.
@param ― string The String object or string literal on which to perform the search.
exec(
const text: any
text);
if (
const match: RegExpExecArray | null
match) {
  const 
const value: string
value = 
const match: RegExpExecArray
match[1];
}

String.prototype.match()

Section titled “String.prototype.match()”
const 
const result: RegExpMatchArray | null
result = "text".
String.match(matcher: {
    [Symbol.match](string: string): RegExpMatchArray | null;
}): RegExpMatchArray | null (+1 overload)
Matches a string or an object that supports being matched against, and returns an array
containing the results of that search, or null if no matches are found.
@param ― matcher An object that supports being matched against.
match(/a(?<foo>b)c/);
if (
const result: RegExpMatchArray | null
result) {
  const 
const value: string
value = 
const result: RegExpMatchArray
result[1];
}

String.prototype.matchAll()

Section titled “String.prototype.matchAll()”
const 
const matches: RegExpStringIterator<RegExpExecArray>
matches = "text".
String.matchAll(regexp: RegExp): RegExpStringIterator<RegExpExecArray>
Matches a string with a regular expression, and returns an iterable of matches
containing the results of that search.
@param ― regexp A variable name or string literal containing the regular expression pattern and flags.
matchAll(/a(?<foo>b)c/g);
for (const 
const match: RegExpExecArray
match of 
const matches: RegExpStringIterator<RegExpExecArray>
matches) {
  const 
const value: string
value = 
const match: RegExpExecArray
match[1];
}

Mixed Named and Unnamed Groups

Section titled “Mixed Named and Unnamed Groups”

When a regex has both named and unnamed capturing groups, only access to the named groups is reported:

const 
const regex: RegExp
regex = /(a)(?<bar>b)c/;
const 
const match: RegExpExecArray | null
match = 
const regex: RegExp
regex.
RegExp.exec(string: string): RegExpExecArray | null
Executes a search on a string using a regular expression pattern, and returns an array containing the results of that search.
@param ― string The String object or string literal on which to perform the search.
exec(
const text: any
text);
if (
const match: RegExpExecArray | null
match) {
  const 
const first: string
first = 
const match: RegExpExecArray
match[1];
  const 
const second: string
second = 
const match: RegExpExecArray
match[2];
}

Valid Uses

Section titled “Valid Uses”

Using named groups correctly:

const 
const regex: RegExp
regex = /a(?<foo>b)c/;
const 
const match: RegExpExecArray | null
match = 
const regex: RegExp
regex.
RegExp.exec(string: string): RegExpExecArray | null
Executes a search on a string using a regular expression pattern, and returns an array containing the results of that search.
@param ― string The String object or string literal on which to perform the search.
exec(
const text: any
text);
if (
const match: RegExpExecArray | null
match) {
  const 
const value: string
value = 
const match: RegExpExecArray
match.
RegExpExecArray.groups?: {
    [key: string]: string;
} | undefined
groups.
string
foo;
}

Accessing unnamed capturing groups by index:

const 
const regex: RegExp
regex = /a(b)c/;
const 
const match: RegExpExecArray | null
match = 
const regex: RegExp
regex.
RegExp.exec(string: string): RegExpExecArray | null
Executes a search on a string using a regular expression pattern, and returns an array containing the results of that search.
@param ― string The String object or string literal on which to perform the search.
exec(
const text: any
text);
if (
const match: RegExpExecArray | null
match) {
  const 
const value: string
value = 
const match: RegExpExecArray
match[1];
}

Accessing match index 0 (the full match):

const 
const regex: RegExp
regex = /a(?<foo>b)c/;
const 
const match: RegExpExecArray | null
match = 
const regex: RegExp
regex.
RegExp.exec(string: string): RegExpExecArray | null
Executes a search on a string using a regular expression pattern, and returns an array containing the results of that search.
@param ― string The String object or string literal on which to perform the search.
exec(
const text: any
text);
if (
const match: RegExpExecArray | null
match) {
  const 
const fullMatch: string
fullMatch = 
const match: RegExpExecArray
match[0];
}

Options

Section titled “Options”

This rule is not configurable.

When Not To Use It

Section titled “When Not To Use It”

If you have a codebase that consistently uses numeric indices for all capturing groups, migrating to named groups may require significant refactoring. You might also prefer to disable this rule if you prefer the brevity of numeric indices over the clarity of named groups.

Further Reading

Section titled “Further Reading”

Equivalents in Other Linters

Section titled “Equivalents in Other Linters”
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