GitHub - tc39/proposal-regexp-modifiers: Regular Expression Pattern Modifiers for ECMAScript (original) (raw)

Regular Expression Pattern Modifiers for ECMAScript

Status

Stage: 4
Champion: Ron Buckton (@rbuckton)

For detailed status of this proposal see TODO, below.

Authors

Motivations

One common capability amongst the majority of regular expression engines that is commonly used by parsers, syntax highlighters, and other tools is the capability to control a subset of regular expression flags such as:

Modifiers are especially helpful when regular expressions are defined in a context where executable code cannot be evaluated, such as a JSON configuration file or TextMate tmLanguage grammar file.

As part of this proposal, we will investigate each existing (and future-proposed) RegExp flag to determine whether they are feasible to used as modifiers.

Prior Art

See https://rbuckton.github.io/regexp-features/features/modifiers.html for additional information.

Syntax

Modifiers allow you to change the currently active RegExp flags within a subexpression.

NOTE: Certain flags cannot be modified mid-expression. These currently include g (global), y (sticky), u (unicode), and d (hasIndices).

NOTE: The actual supported flags will be determined on a case-by-case basis. See #1.

NOTE: This has no conflicts with existing syntax, as ECMAScript currently produces an error for this syntax in both u and non-u modes.

NOTE: The "self-bounded" form ((?imsx-imsx:subexpression)) advanced to Stage 2 on December 15th, 2021.

NOTE: The "unbounded" form ((?imsx-imsx)) is no longer being considered as part of this proposal as of December 15th, 2021.

Examples

const re1 = /^a-z$/i; re1.test("ab"); // true re1.test("Ab"); // true re1.test("aB"); // false

const re2 = /^(?i:[a-z])[a-z]$/; re2.test("ab"); // true re2.test("Ab"); // true re2.test("aB"); // false

History

TODO

The following is a high-level list of tasks to progress through each stage of the TC39 proposal process:

Stage 1 Entrance Criteria

Stage 2 Entrance Criteria

Stage 2.7 Entrance Criteria

Stage 3 Entrance Criteria

Stage 4 Entrance Criteria