boris/node_modules/mdast-util-to-markdown/lib/util/compile-pattern.js

/**
 * @import {CompilePattern} from '../types.js'
 */

/**
 * @type {CompilePattern}
 */
export function compilePattern(pattern) {
  if (!pattern._compiled) {
    const before =
      (pattern.atBreak ? '[\\r\\n][\\t ]*' : '') +
      (pattern.before ? '(?:' + pattern.before + ')' : '')

    pattern._compiled = new RegExp(
      (before ? '(' + before + ')' : '') +
        (/[|\\{}()[\]^$+*?.-]/.test(pattern.character) ? '\\' : '') +
        pattern.character +
        (pattern.after ? '(?:' + pattern.after + ')' : ''),
      'g'
    )
  }

  return pattern._compiled
}