no-proto

Disallow the use of the __proto__ property

__proto__ property has been deprecated as of ECMAScript 3.1 and shouldn’t be used in the code. Use Object.getPrototypeOf and Object.setPrototypeOf instead.

Rule Details

When an object is created with the new operator, __proto__ is set to the original “prototype” property of the object’s constructor function. Object.getPrototypeOf is the preferred method of getting the object’s prototype. To change an object’s prototype, use Object.setPrototypeOf.

Examples of incorrect code for this rule:

/*eslint no-proto: "error"*/

var a = obj.__proto__;

var a = obj["__proto__"];

obj.__proto__ = b;

obj["__proto__"] = b;
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Examples of correct code for this rule:

/*eslint no-proto: "error"*/

var a = Object.getPrototypeOf(obj);

Object.setPrototypeOf(obj, b);

var c = { __proto__: a };
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When Not To Use It

You might want to turn this rule off if you need to support legacy browsers which implement the __proto__ property but not Object.getPrototypeOf or Object.setPrototypeOf.

Version

This rule was introduced in ESLint v0.0.9.

Further Reading

John Resig - Object.getPrototypeOf
johnresig.com

Resources

• Rule source
• Tests source