objectProto

Reports using the deprecated proto property to access or modify an object's prototype.

✅ This rule is included in the ts untyped presets.

The __proto__ property is a deprecated way to access and modify an object’s prototype. While it is supported for backwards compatibility, it is not part of the ECMAScript standard and can cause performance issues. Direct manipulation of an object’s prototype can lead to “hidden classes” in JavaScript engines, resulting in slower code execution.

Examples

❌ Incorrect

const proto = obj.__proto__;

obj.__proto__ = prototype;

const value = obj["__proto__"];

✅ Correct

const proto = Object.getPrototypeOf(obj);

Object.setPrototypeOf(obj, prototype);

const obj = Object.create(prototype);

Options

This rule is not configurable.

When Not To Use It

If you need to support very old JavaScript environments that don’t have Object.getPrototypeOf and Object.setPrototypeOf (pre-ES5), you might need to disable this rule. However, this is extremely rare in modern development, as even Internet Explorer 9 supports these methods.

Further Reading

• MDN: Object.prototype.proto
• MDN: Object.getPrototypeOf()
• MDN: Object.setPrototypeOf()
• MDN: Object.create()

Equivalents in Other Linters

• ESLint: no-proto
• Oxlint: eslint/no-proto