constructorReturns

Reports returning values from constructor functions.

✅ This rule is included in the ts untyped presets.

In JavaScript, returning a value from a constructor overrides the newly created instance. This behavior is generally unintentional and can lead to unexpected results where the returned value becomes the result of the new expression instead of the instance.

While JavaScript technically allows this, it’s generally a code smell that indicates a design issue. If you need to return a different object based on constructor parameters, consider using a factory function instead.

Examples

❌ Incorrect

class Example {
  constructor() {
    return {};
  }
}

class SpecialValue {
  constructor(value: number) {
    if (value < 0) {
      return null;
Error ts(2322)  ― Type 'null' is not assignable to type 'SpecialValue'.
Error ts(2409)  ― Return type of constructor signature must be assignable to the instance type of the class.
    }
    this.value = value;
Error ts(2339)  ― Property 'value' does not exist on type 'SpecialValue'.
  }
}

✅ Correct

class Example {
  constructor() {
    this.value = 42;
Error ts(2339)  ― Property 'value' does not exist on type 'Example'.
  }
}

class SpecialValue {
  constructor(value: number) {
    if (value < 0) {
      throw new Error("Value must be non-negative");
    }
    this.value = value;
Error ts(2339)  ― Property 'value' does not exist on type 'SpecialValue'.
  }
}

Options

This rule is not configurable.

When Not To Use It

If you have a rare use case where you intentionally need to return different objects from a constructor, you might choose to disable this rule for those specific cases. However, this is generally considered an anti-pattern, and you should strongly consider refactoring to use a factory function instead.

Further Reading

• MDN: Constructor
• MDN: Factory Functions
• JavaScript Info: Class patterns

Equivalents in Other Linters

• Biome: noConstructorReturn
• ESLint: no-constructor-return
• Oxlint: eslint/no-constructor-return