stringStartsEndsWith

Reports regex patterns that can be replaced with endsWith or startsWith.

✅ This rule is included in the ts stylistic presets.

Regular expressions with simple ^ or $ anchors can be replaced with the more readable and performant startsWith() and endsWith() string methods.

This rule detects regex .test() calls that check for simple string prefixes or suffixes and suggests using the dedicated string methods instead.

Examples

const 
const hasPrefix: boolean
hasPrefix = /^foo/.
RegExp.test(string: string): boolean
Returns a Boolean value that indicates whether or not a pattern exists in a searched string.
@param ― string String on which to perform the search.
test(
const str: string
str);

const 
const hasPrefix: boolean
hasPrefix = 
const str: string
str.
String.startsWith(searchString: string, position?: number): boolean
Returns true if the sequence of elements of searchString converted to a String is the
same as the corresponding elements of this object (converted to a String) starting at
position. Otherwise returns false.
startsWith("foo");

Suffix Check with $

❌ Incorrect
✅ Correct

const 
const hasSuffix: boolean
hasSuffix = /bar$/.
RegExp.test(string: string): boolean
Returns a Boolean value that indicates whether or not a pattern exists in a searched string.
@param ― string String on which to perform the search.
test(
const str: string
str);

const 
const hasSuffix: boolean
hasSuffix = 
const str: string
str.
String.endsWith(searchString: string, endPosition?: number): boolean
Returns true if the sequence of elements of searchString converted to a String is the
same as the corresponding elements of this object (converted to a String) starting at
endPosition – length(this). Otherwise returns false.
endsWith("bar");

Options

This rule is not configurable.

When Not To Use It

If you need case-insensitive matching or other regex features, the string methods won’t work as direct replacements. This rule ignores patterns with the i (case-insensitive) or m (multiline) flags.

Equivalents in Other Linters

ESLint: @typescript-eslint/prefer-string-starts-ends-with
Oxlint: unicorn/prefer-string-starts-ends-with

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