var toObject = require('../internals/to-object'); var floor = Math.floor; var replace = ''.replace; var SUBSTITUTION_SYMBOLS = /\$([$&'`]|\d{1,2}|<[^>]*>)/g; var SUBSTITUTION_SYMBOLS_NO_NAMED = /\$([$&'`]|\d{1,2})/g; // `GetSubstitution` abstract operation // https://tc39.es/ecma262/#sec-getsubstitution module.exports = function (matched, str, position, captures, namedCaptures, replacement) { var tailPos = position + matched.length; var m = captures.length; var symbols = SUBSTITUTION_SYMBOLS_NO_NAMED; if (namedCaptures !== undefined) { namedCaptures = toObject(namedCaptures); symbols = SUBSTITUTION_SYMBOLS; } return replace.call(replacement, symbols, function (match, ch) { var capture; switch (ch.charAt(0)) { case '$': return '$'; case '&': return matched; case '`': return str.slice(0, position); case "'": return str.slice(tailPos); case '<': capture = namedCaptures[ch.slice(1, -1)]; break; default: // \d\d? var n = +ch; if (n === 0) return match; if (n > m) { var f = floor(n / 10); if (f === 0) return match; if (f <= m) return captures[f - 1] === undefined ? ch.charAt(1) : captures[f - 1] + ch.charAt(1); return match; } capture = captures[n - 1]; } return capture === undefined ? '' : capture; }); };