get-substitution.js
1.32 KB
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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;
// 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;
});
};