@studnicky/v8/regexp-in-loops

Disallows new RegExp(...) or RegExp(...) inside any loop body. Constructing a RegExp object on every iteration allocates a new object and recompiles the pattern. Hoist the regexp to the outer scope and reuse it.

Fixable: No · Options: No · Suggested severity: error

✗ Incorrect

for (const line of lines) {
  const re = new RegExp(pattern);
  if (re.test(line)) { results.push(line); }
}

for (let i = 0; i < items.length; i++) {
  if (RegExp('^prefix').test(items[i] ?? '')) { match(items[i]); }
}

✓ Correct

// Hoist the RegExp outside the loop
const re = new RegExp(pattern);
for (const line of lines) {
  if (re.test(line)) { results.push(line); }
}

// Regex literals are already compiled at parse time
const PREFIX_RE = /^prefix/;
for (let i = 0; i < items.length; i++) {
  if (PREFIX_RE.test(items[i] ?? '')) { match(items[i]); }
}