no-negated-conjunction.md

no-negated-conjunction

Transforms the negation of a conjunction into the equivalent disjunction of negations according to De Morgan’s first law.

Rule Details

This rule enforces that when a conjunction is negated, the expression is rewritten according to De Morgan’s law. Instead of writing a negated conjunction like:

if (!(a && b)) {
  /* ... */
}

The rule suggests (and can auto-fix) the equivalent form:

if (!a || !b) {
  /* ... */
}

Why Use This Rule?

Negated conjunctions can sometimes be harder to read and understand. Transforming them into a disjunction of negations makes the logic explicit:

• It clearly shows that at least one of the conditions must be false.
• It may help avoid mistakes in complex boolean logic.

When Is the Rule Applied?

• The rule applies only when the operand of the negation is a pure conjunction — that is, when all operands are combined with && at the same nesting level.
• If the expression inside the negation contains a mix of logical operators (for example, !(a && b || c)), the rule will not apply the transformation.

Auto-fix

This rule is auto-fixable. When applied, it automatically rewrites code such as:

const foo = !(a && !b && c >= 10)

To:

const foo = !a || b || c < 10

Options

This rule has no options.

Related Rules

• no-negated-disjunction — A similar rule for transforming the negation of a disjunction (!(A || B)) into the equivalent conjunction of negations (!A && !B), based on De Morgan’s second law.

Resources

• Rule Source
• Test Source