@putout/plugin-simplify-logical-expressions

The logical NOT (!) operator takes truth to falsity and vice versa.

(c) MDN

🐊Putout plugin adds ability to simplify logical expressions containing comparisons which will always evaluate to true or false since it's likely indications of programmer error. Complements @putout/plugin-apply-comparison-order. Merged to @putout/plugin-logical-expressions.

Install

npm i @putout/plugin-simplify-logical-expressions -D

Rule

{
    "rules": {
        "simplify-logical-expressions": "on"
    }
}

❌ Example of incorrect code

const is = !(options && !options.bidirectional);

if (!left.type === 'UnaryExpression');

const oneOf = a || a;
const same = a === a;

✅ Example of correct code

const is = !options || options.bidirectional;

if (left.type !== 'UnaryExpression');

const oneOf = a;
const same = true;

The rule also simplify duplication use:

-if (a && b || a && c) {
+if (a && (b || c)) {
}

Wrong cases with instanceof:

-!a instanceof b;
-a instanceof !b;
-!a instanceof !b;
+!(a instanceof b);

Wrong cases with in:

-!a in b;
-a in !b;
+!(a in b);

In case of duplicates:

-a && b && a
+a && b

Comparison

Linter	Rule	Fix
🐊 Putout	simplify-logical-expressions	✅
⏣ ESLint	no-constant-binary-expression	❌

License

MIT