eslint-prototype-chain

ESLint rule to optimize prototype chain lookups

Summary

Repeatedly looking up values deep in the prototype chain can be less-than-performant--especially if getters are defined. Creating a variable to reference the value can speed things up.

This ESLint rule will tell you if you're doing this too much.

Installation

$ npm install -D eslint eslint-plugin-prototype-chain

Usage

Add this to your .eslintrc, assuming it's a JSON file:

{
  "plugins": [
    "prototype-chain"
  ],
  "prototype-chain/prototype-chain": [2, 1, 1]
}

The above configuration will cause an ESLint error when, in the same scope:

• You use the same object member expression (foo.bar) OR the same "this" expression (this.bar) more than one (1) time (that's the 2nd array item), AND
• You use one (1) member in the chain

A configuration such as this:

{
  "prototype-chain/prototype-chain": [2, 2, 3]
}

would cause an ESLint error when, in the same scope:

• You use the same object member expression (foo.bar) OR the same "this" expression (this.bar) more than one (2) times, AND
• You use one (2) members in the chain

That means repeating foo.bar will not throw an error. Repeating foo.bar.baz one time will not cause an error, but repeating it two times will.

Hope that makes sense!

Fair Warning

There are tests, but I haven't tried this against much real-world code yet.

License

© 2015 Christopher Hiller. Licensed MIT.