@std/regexp

Overview Jump to heading#

Functions for tasks related to regular expression (regexp), such as escaping text for interpolation into a regexp.

import { escape } from "@std/regexp/escape";
import { assertEquals, assertMatch, assertNotMatch } from "@std/assert";

const re = new RegExp(`^${escape(".")}$`, "u");

assertEquals("^\\.$", re.source);
assertMatch(".", re);
assertNotMatch("a", re);

Add to your project Jump to heading#

deno add jsr:@std/regexp

See all symbols in @std/regexp on

What is RegExp? Jump to heading#

RegExp (regular expressions) are patterns used to match character combinations in strings. In JavaScript, they are implemented via the RegExp object and literal syntax (e.g., /pattern/flags).

Why use @std/regexp? Jump to heading#

This package provides small utilities to make working with regexps safer and easier:

• Use escape() when interpolating user input into a RegExp to avoid unintended meta-characters.
• Prefer the u (unicode) flag for correctness; it changes how escapes and character classes behave.
• Anchors: ^ and $ match start/end of string; use m flag to make them line-based.
• When performance matters, precompile your regex once and reuse it.

Examples Jump to heading#

import { escape } from "@std/regexp/escape";

const user = "hello.+(world)";
const safe = new RegExp(`^${escape(user)}$`, "u");
safe.test("hello.+(world)"); // true
safe.test("helloX(world)"); // false

// Multiline anchors
const re = /^error:.+$/mu;
re.test("ok\nerror: bad\nnext"); // true