eslint-plugin-const-immutable

This plugin forces all const declarations to be immutable. Ecmascript 6 don't allow variables declared with const to be reassigned, but doesn't necassarilly avoid mutation to the strucutures the respective variable is pointing to.

Installation

You'll first need to install ESLint:

$ npm i eslint --save-dev

Next, install eslint-plugin-const-immutable:

$ npm install eslint-plugin-const-immutable --save-dev

Note: If you installed ESLint globally (using the -g flag) then you must also install eslint-plugin-const-immutable globally.

Usage

Add const-immutable to the plugins section of your .eslintrc configuration file. You can omit the eslint-plugin- prefix:

{
    "plugins": [
        "const-immutable"
    ]
}

Then configure the rules you want to use under the rules section.

{
    "rules": {
        "const-immutable/no-mutation": 2
    }
}

Supported Rules

no-mutation

This rule forces the variables declared with const to remain immutable. The following code are considered problematic.

const y = 1;
y = 2;             // error

const y = {a: { b: 'c' }};
y.a.b = 2;         // error

const y = {a: { b: 'c' }};
function foo() {
  if (true) {
    y.a.b = 2;     // error
  }
}

const obj = { a: '1', b: '2' };
const {a,b} = obj;
a += 1;            // error

const obj = { a: '1' };
delete obj.a;     // error

const obj = { a: '1' };
Object.assign(obj, {a: '2'});     // error

Sample Configuration File

{
    "extends": "airbnb",
    "plugins": [
        "const-immutable"
    ],
    "rules": {
        "const-immutable/no-mutation": 2
    }
}