@studnicky/v8/for-in-loops

for...in enumerates string keys including inherited ones, triggers deoptimization on objects with non-enumerable or accessor properties, and produces string keys even when integer indexing is expected. Use Object.keys(), Object.values(), or Object.entries() instead.

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

✗ Incorrect

for (const key in obj) {
  process(key, obj[key]);
}

for (const key in config) {
  if (Object.prototype.hasOwnProperty.call(config, key)) {
    apply(key, config[key]);
  }
}

✓ Correct

for (const [key, value] of Object.entries(obj)) {
  process(key, value);
}

for (const key of Object.keys(config)) {
  apply(key, config[key]);
}