eslint-plugin-void-only-side-effects

The void operator can be used to ensure side effects don't leak return values.

const mutationCallback = value => void (object.field = value);

The void operator can also be abused to write expressions that are nothing more than undefined with extra steps.

const isUndefined = value => value === void 0;

This plugin enables the rule "void-only-side-effects" which disallows the latter use.

Code can be automatically fixed with --fix. The above example would be fixed to

const isUndefined = value => value === undefined;

If your code editor supports eslint suggestions, the rule will allow you to apply the fix through a suggestion.

Usage

Install package.

npm install eslint-plugin-void-only-side-effects --save-dev

In .eslintrc

"plugins": [
  "void-only-side-effects"
],
"rules": [
  "void-only-side-effects/void-only-side-effects": {severity}
]

Where severity is "error" or "warn".

Verified in eslint version 7.6.0. Older versions may require different configurations.

Default

By default the void operator is only allowed to be used with arguments that could potentially have side effects.

Examples of correct code for this rule

void functionCall();

void (object.field = value);

Examples of incorrect code for this rule

void 0;

void (() => functionCall());

allowTraps

The rule can be configured to allow arguments that may potentially trigger traps.

To allow all traps configure "allowTraps": true.

rules: [
  "void-only-side-effects/void-only-side-effects": [{severity}, { "allowTraps": true }]
]

To allow select traps configure "allowTraps": {object}.

rules: [
  "void-only-side-effects/void-only-side-effects": [
    {severity},
    {
      "allowTraps": {
        "get": {boolean},
        "has": {boolean},
        "ownKeys": {boolean}
      }
    }
  ]
]

You can omit false values from the configuration object.

Examples of correct code for this option

void object.field; // get

void 'field' in object; // has

void { ...object }; // ownKeys