eslint/rules/conditions

Conditions: if / else, ternaries, booleans, comparisons, equality and switch: explicit, simple and exhaustive branches. Rules of ESLint, typescript-eslint and SonarJS (the Sonar way profile of SonarQube) on this subject, every rule listed; the TypeScript rules apply to TypeScript files only.

60 rules, 43 on. Source: lint/eslint/rules/conditions.mjs.

Rule	Setting	Files	What it checks	Why
no-compare-neg-zero	error	JS + TS	Disallow comparing against -0	—
no-cond-assign	error	JS + TS	Disallow assignment operators in conditional expressions	—
no-constant-binary-expression	error	JS + TS	Disallow expressions where the operation doesn't affect the value	—
no-constant-condition	error	JS + TS	Disallow constant expressions in conditions	—
no-dupe-else-if	error	JS + TS	Disallow duplicate conditions in if-else-if chains	—
no-duplicate-case	error	JS + TS	Disallow duplicate case labels	—
no-fallthrough	error	JS + TS	Disallow fallthrough of case statements	Off: TypeScript noFallthroughCasesInSwitch covers it.
no-self-compare	error	JS + TS	Disallow comparisons where both sides are exactly the same	—
no-template-curly-in-string	error	JS + TS	Disallow template literal placeholder syntax in regular strings	—
no-unmodified-loop-condition	error	JS + TS	Disallow unmodified loop conditions	—
no-unsafe-negation	error	JS + TS	Disallow negating the left operand of relational operators	—
no-unsafe-optional-chaining	error	JS + TS	Disallow use of optional chaining in contexts where the undefined value is not allowed	—
camelcase	off	JS + TS	Enforce camelcase naming convention	Off: replaced by @typescript-eslint/naming-convention.
curly	error, "all"	JS + TS	Enforce consistent brace style for all control statements	Braces on every block: smaller diffs, the only option safe with Prettier.
default-case	off	JS + TS	Require default cases in switch statements	Off: @typescript-eslint/switch-exhaustiveness-check covers it.
default-case-last	info	JS + TS	Enforce default clauses in switch statements to be last	—
eqeqeq	error	JS + TS	Require the use of === and !==	—
logical-assignment-operators	error	JS + TS	Require or disallow logical assignment operator shorthand	—
no-case-declarations	error	JS + TS	Disallow lexical declarations in case clauses	—
no-else-return	error	JS + TS	Disallow else blocks after return statements in if statements	—
no-eq-null	off	JS + TS	Disallow null comparisons without type-checking operators	Off: eqeqeq already forbids == null.
no-extra-boolean-cast	error	JS + TS	Disallow unnecessary boolean casts	—
no-lonely-if	error	JS + TS	Disallow if statements as the only statement in else blocks	—
no-negated-condition	info	JS + TS	Disallow negated conditions	—
no-nested-ternary	warn	JS + TS	Disallow nested ternary expressions	—
no-ternary	off	JS + TS	Disallow ternary operators	—
no-unneeded-ternary	error	JS + TS	Disallow ternary operators when simpler alternatives exist	—
yoda	error	JS + TS	Require or disallow "Yoda" conditions	—
sonarjs/no-nested-switch	off	JS + TS	"switch" statements should not be nested	Off: not in the Sonar way profile of SonarQube.
sonarjs/strings-comparison	off	JS + TS	Comparison operators should not be used with strings	Off: not in the Sonar way profile of SonarQube.
sonarjs/no-case-label-in-switch	off	JS + TS	"switch" statements should not contain non-case labels	Off: duplicate of no-labels.
sonarjs/no-fallthrough	off	JS + TS	Switch cases should end with an unconditional "break" statement	Off: duplicate of no-fallthrough.
sonarjs/no-gratuitous-expressions	off	JS + TS	Boolean expressions should not be gratuitous	Off: duplicate of @typescript-eslint/no-unnecessary-condition.
sonarjs/no-identical-conditions	off	JS + TS	"if/else if" chains and "switch" cases should not have the same condition	Off: duplicate of no-dupe-else-if and no-duplicate-case.
sonarjs/no-nested-conditional	off	JS + TS	Ternary operators should not be nested	Off: duplicate of no-nested-ternary.
sonarjs/no-redundant-boolean	off	JS + TS	Boolean literals should not be used in comparisons	Off: duplicate of @typescript-eslint/no-unnecessary-boolean-literal-compare.
sonarjs/comma-or-logical-or-case	error	JS + TS	Comma and logical OR operators should not be used in switch cases	—
sonarjs/conditional-indentation	off	JS + TS	A conditionally executed single line should be denoted by indentation	Off: not in the Sonar way profile of SonarQube.
sonarjs/different-types-comparison	warn	JS + TS	Strict equality operators should not be used with dissimilar types	Warn: false positives on narrowed union types.
sonarjs/elseif-without-else	off	JS + TS	"if ... else if" constructs should end with "else" clauses	Off: not in the Sonar way profile of SonarQube.
sonarjs/index-of-compare-to-positive-number	warn	JS + TS	"indexOf" checks should not be for positive numbers	—
sonarjs/max-switch-cases	warn	JS + TS	"switch" statements should not have too many "case" clauses	—
sonarjs/no-all-duplicated-branches	error	JS + TS	All branches in a conditional structure should not have exactly the same implementation	—
sonarjs/no-collapsible-if	off	JS + TS	Mergeable "if" statements should be combined	Off: not in the Sonar way profile of SonarQube.
sonarjs/no-duplicated-branches	warn	JS + TS	Two branches in a conditional structure should not have exactly the same implementation	—
sonarjs/no-equals-in-for-termination	warn	JS + TS	Equality operators should not be used in "for" loop termination conditions	—
sonarjs/no-identical-expressions	error	JS + TS	Identical expressions should not be used on both sides of a binary operator	—
sonarjs/no-inverted-boolean-check	warn	JS + TS	Boolean checks should not be inverted	—
sonarjs/no-same-line-conditional	warn	JS + TS	Conditionals should start on new lines	—
sonarjs/no-small-switch	warn	JS + TS	"if" statements should be preferred over "switch" when simpler	—
sonarjs/prefer-single-boolean-return	warn	JS + TS	Return of boolean expressions should not be wrapped into an "if-then-else" statement	—
no-fallthrough	off	TS	Disallow fallthrough of case statements	Off: TypeScript noFallthroughCasesInSwitch covers it.
no-unsafe-negation	off	TS	Disallow negating the left operand of relational operators	—
@typescript-eslint/no-unnecessary-boolean-literal-compare	error	TS	Disallow unnecessary equality comparisons against boolean literals	—
@typescript-eslint/no-unnecessary-condition	warn, {"allowConstantLoopConditions":true}	TS	Disallow conditionals where the type is always truthy or always falsy	while (true) is allowed.
@typescript-eslint/no-unsafe-enum-comparison	error	TS	Disallow comparing an enum value with a non-enum value	—
@typescript-eslint/prefer-nullish-coalescing	info, {"ignorePrimitives":{"string":true}}	TS	Enforce using the nullish coalescing operator instead of logical assignments or chaining	Custom: str || 'default' stays allowed to also replace empty strings.
@typescript-eslint/prefer-optional-chain	error	TS	Enforce using concise optional chain expressions instead of chained logical ands, negated logical ors, or empty objects	—
@typescript-eslint/strict-boolean-expressions	warn, {"allowNumber":false,"allowNullableBoolean":true,"allowNu…	TS	Disallow certain types in boolean expressions	Custom: only numbers must be compared explicitly (count > 0).
@typescript-eslint/switch-exhaustiveness-check	error, {"considerDefaultExhaustiveForUnions":true}	TS	Require switch-case statements to be exhaustive	Custom: a default case covers the remaining members.