eslint/no-extra-boolean-cast Correctness

✅ This rule is turned on by default.

🛠️ 💡 An auto-fix and a suggestion are available for this rule for some violations.

What it does

This rule disallows unnecessary boolean casts.

Why is this bad?

In contexts such as an if statement's test where the result of the expression will already be coerced to a Boolean, casting to a Boolean via double negation (!!) or a Boolean call is unnecessary.

Examples

Examples of incorrect code for this rule:

javascript

var foo = !!!bar;
var foo = Boolean(!!bar);

if (!!foo) {
}
if (Boolean(foo)) {
}

// with "enforceForInnerExpressions" option enabled
if (!!foo || bar) {
}

Examples of correct code for this rule:

javascript

var foo = !bar;
var foo = Boolean(bar);

if (foo) {
}
if (foo) {
}

// with "enforceForInnerExpressions" option enabled
if (foo || bar) {
}

Configuration

This rule accepts a configuration object with the following properties:

enforceForInnerExpressions

type: boolean

default: false

when set to true, in addition to checking default contexts, checks whether extra boolean casts are present in expressions whose result is used in a boolean context. See examples below. Default is false, meaning that this rule by default does not warn about extra booleans cast inside inner expressions.

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)Config (oxlint.config.ts)CLI

json

{
  "rules": {
    "no-extra-boolean-cast": "error"
  }
}

import { defineConfig } from "oxlint";

export default defineConfig({
  rules: {
    "no-extra-boolean-cast": "error",
  },
});

bash

oxlint --deny no-extra-boolean-cast

Version

This rule was added in v0.0.8.

What it does ​

Why is this bad? ​

Examples ​

Configuration ​

enforceForInnerExpressions ​

How to use ​

Version ​

References ​