complete/no-for-in

💼 This rule is enabled in the ✅ recommended config.

📝 Disallows “for x in y” statements.

Rule Details

“for in” loops iterate over the entire prototype chain, which is virtually never what you want. Use a “for of” loop or instead.

// Bad
const array = [1, 2, 3];
for (const element in array) {
}

// Good
const array = [1, 2, 3];
for (const element of array) {
}

// Bad
const object = { foo: "bar" };
for (const key in object) {
}

// Good
const object = { foo: "bar" };
for (const key of Object.keys(object)) {
}

Options

This rule is not configurable.

Resources

• How to use this rule
• Rule source
• Test source