JavaScript Rules

Below the list of rules supported by Biome, divided by group. Here’s a legend of the emojis:

• The icon indicates that the rule is part of the recommended rules.
• The icon indicates that the rule provides a code action (fix) that is safe to apply.
• The icon indicates that the rule provides a code action (fix) that is unsafe to apply.
• The icon indicates that the rule has been implemented and scheduled for the next release.

Rule name	Description	Properties
noAccessKey	Enforce that the accessKey attribute is not used on any HTML element.
noAriaHiddenOnFocusable	Enforce that aria-hidden=“true” is not set on focusable elements.
noAriaUnsupportedElements	Enforce that elements that do not support ARIA roles, states, and properties do not have those attributes.
noAutofocus	Enforce that autoFocus prop is not used on elements.
noDistractingElements	Enforces that no distracting elements are used.
noHeaderScope	The scope prop should be used only on <th> elements.
noInteractiveElementToNoninteractiveRole	Enforce that non-interactive ARIA roles are not assigned to interactive HTML elements.
noLabelWithoutControl	Enforce that a label element or component has a text label and an associated input.
noNoninteractiveElementInteractions	Disallow use event handlers on non-interactive elements.
noNoninteractiveElementToInteractiveRole	Enforce that interactive ARIA roles are not assigned to non-interactive HTML elements.
noNoninteractiveTabindex	Enforce that tabIndex is not assigned to non-interactive HTML elements.
noPositiveTabindex	Prevent the usage of positive integers on tabIndex property
noRedundantAlt	Enforce img alt prop does not contain the word “image”, “picture”, or “photo”.
noRedundantRoles	Enforce explicit role property is not the same as implicit/default role property on an element.
noStaticElementInteractions	Enforce that static, visible elements (such as <div>) that have click handlers use the valid role attribute.
noSvgWithoutTitle	Enforces the usage of the title element for the svg element.
useAltText	Enforce that all elements that require alternative text have meaningful information to relay back to the end user.
useAnchorContent	Enforce that anchors have content and that the content is accessible to screen readers.
useAriaActivedescendantWithTabindex	Enforce that tabIndex is assigned to non-interactive HTML elements with aria-activedescendant.
useAriaPropsForRole	Enforce that elements with ARIA roles must have all required ARIA attributes for that role.
useAriaPropsSupportedByRole	Enforce that ARIA properties are valid for the roles that are supported by the element.
useButtonType	Enforces the usage of the attribute type for the element button
useFocusableInteractive	Elements with an interactive role and interaction handlers must be focusable.
useHeadingContent	Enforce that heading elements (h1, h2, etc.) have content and that the content is accessible to screen readers. Accessible means that it is not hidden using the aria-hidden prop.
useHtmlLang	Enforce that html element has lang attribute.
useIframeTitle	Enforces the usage of the attribute title for the element iframe.
useKeyWithClickEvents	Enforce onClick is accompanied by at least one of the following: onKeyUp, onKeyDown, onKeyPress.
useKeyWithMouseEvents	Enforce onMouseOver / onMouseOut are accompanied by onFocus / onBlur.
useMediaCaption	Enforces that audio and video elements must have a track for captions.
useSemanticElements	It detects the use of role attributes in JSX elements and suggests using semantic elements instead.
useValidAnchor	Enforce that all anchors are valid, and they are navigable elements.
useValidAriaProps	Ensures that ARIA properties aria-* are all valid.
useValidAriaRole	Elements with ARIA roles must use a valid, non-abstract ARIA role.
useValidAriaValues	Enforce that ARIA state and property values are valid.
useValidAutocomplete	Use valid values for the autocomplete attribute on input elements.
useValidLang	Ensure that the attribute passed to the lang attribute is a correct ISO language and/or country.

Rule name	Description	Properties
noAdjacentSpacesInRegex	Disallow unclear usage of consecutive space characters in regular expression literals
noArguments	Disallow the use of arguments.
noBannedTypes	Disallow primitive type aliases and misleading types.
noCommaOperator	Disallow comma operator.
noEmptyTypeParameters	Disallow empty type parameters in type aliases and interfaces.
noExcessiveCognitiveComplexity	Disallow functions that exceed a given Cognitive Complexity score.
noExcessiveLinesPerFunction	Restrict the number of lines of code in a function.
noExcessiveNestedTestSuites	This rule enforces a maximum depth to nested describe() in test files.
noExtraBooleanCast	Disallow unnecessary boolean casts
noFlatMapIdentity	Disallow to use unnecessary callback on flatMap.
noForEach	Prefer for...of statement instead of Array.forEach.
noImplicitCoercions	Disallow shorthand type conversions.
noStaticOnlyClass	This rule reports when a class has no non-static members, such as for a class used exclusively as a static namespace.
noThisInStatic	Disallow this and super in static contexts.
noUselessCatch	Disallow unnecessary catch clauses.
noUselessConstructor	Disallow unnecessary constructors.
noUselessContinue	Avoid using unnecessary continue.
noUselessEmptyExport	Disallow empty exports that don’t change anything in a module file.
noUselessEscapeInRegex	Disallow unnecessary escape sequence in regular expression literals.
noUselessFragments	Disallow unnecessary fragments
noUselessLabel	Disallow unnecessary labels.
noUselessLoneBlockStatements	Disallow unnecessary nested block statements.
noUselessRename	Disallow renaming import, export, and destructured assignments to the same name.
noUselessStringConcat	Disallow unnecessary concatenation of string or template literals.
noUselessStringRaw	Disallow unnecessary String.raw function in template string literals without any escape sequence.
noUselessSwitchCase	Disallow useless case in switch statements.
noUselessTernary	Disallow ternary operators when simpler alternatives exist.
noUselessThisAlias	Disallow useless this aliasing.
noUselessTypeConstraint	Disallow using any or unknown as type constraint.
noUselessUndefinedInitialization	Disallow initializing variables to undefined.
noVoid	Disallow the use of void operators, which is not a familiar operator.
useArrowFunction	Use arrow functions over function expressions.
useDateNow	Use Date.now() to get the number of milliseconds since the Unix Epoch.
useFlatMap	Promotes the use of .flatMap() when map().flat() are used together.
useIndexOf	Prefer Array#{indexOf,lastIndexOf}() over Array#{findIndex,findLastIndex}() when looking for the index of an item.
useLiteralKeys	Enforce the usage of a literal access to properties over computed property access.
useNumericLiterals	Disallow parseInt() and Number.parseInt() in favor of binary, octal, and hexadecimal literals
useOptionalChain	Enforce using concise optional chain instead of chained logical expressions.
useRegexLiterals	Enforce the use of the regular expression literals instead of the RegExp constructor if possible.
useSimpleNumberKeys	Disallow number literal object member names which are not base 10 or use underscore as separator.
useSimplifiedLogicExpression	Discard redundant terms from logical expressions.
useWhile	Enforce the use of while loops instead of for loops when the initializer and update expressions are not needed.

Rule name	Description	Properties
noChildrenProp	Prevent passing of children as props.
noConstAssign	Prevents from having const variables being re-assigned.
noConstantCondition	Disallow constant expressions in conditions
noConstantMathMinMaxClamp	Disallow the use of Math.min and Math.max to clamp a value where the result itself is constant.
noConstructorReturn	Disallow returning a value from a constructor.
noEmptyCharacterClassInRegex	Disallow empty character classes in regular expression literals.
noEmptyPattern	Disallows empty destructuring patterns.
noGlobalDirnameFilename	Disallow the use of __dirname and __filename in the global scope.
noGlobalObjectCalls	Disallow calling global object properties as functions
noInnerDeclarations	Disallow function and var declarations that are accessible outside their block.
noInvalidBuiltinInstantiation	Ensure that builtins are correctly instantiated.
noInvalidConstructorSuper	Prevents the incorrect use of super() inside classes. It also checks whether a call super() is missing from classes that extends other constructors.
noInvalidUseBeforeDeclaration	Disallow the use of variables, function parameters, classes, and enums before their declaration
noNestedComponentDefinitions	Disallows defining React components inside other components.
noNodejsModules	Forbid the use of Node.js builtin modules.
noNonoctalDecimalEscape	Disallow \8 and \9 escape sequences in string literals.
noPrecisionLoss	Disallow literal numbers that lose precision
noPrivateImports	Restrict imports of private exports.
noProcessGlobal	Disallow the use of process global.
noQwikUseVisibleTask	Disallow useVisibleTask$() functions in Qwik components.
noReactPropAssignments	Disallow assigning to React component props.
noRenderReturnValue	Prevent the usage of the return value of React.render.
noRestrictedElements	Disallow the use of configured elements.
noSelfAssign	Disallow assignments where both sides are exactly the same.
noSetterReturn	Disallow returning a value from a setter
noSolidDestructuredProps	Disallow destructuring props inside JSX components in Solid projects.
noStringCaseMismatch	Disallow comparison of expressions modifying the string case with non-compliant value.
noSwitchDeclarations	Disallow lexical declarations in switch clauses.
noUndeclaredDependencies	Disallow the use of dependencies that aren’t specified in the package.json.
noUndeclaredVariables	Prevents the usage of variables that haven’t been declared inside the document.
noUnreachable	Disallow unreachable code
noUnreachableSuper	Ensures the super() constructor is called exactly once on every code path in a class constructor before this is accessed if the class has a superclass
noUnsafeFinally	Disallow control flow statements in finally blocks.
noUnsafeOptionalChaining	Disallow the use of optional chaining in contexts where the undefined value is not allowed.
noUnusedFunctionParameters	Disallow unused function parameters.
noUnusedImports	Disallow unused imports.
noUnusedLabels	Disallow unused labels.
noUnusedPrivateClassMembers	Disallow unused private class members
noUnusedVariables	Disallow unused variables.
noVoidElementsWithChildren	This rules prevents void elements (AKA self-closing elements) from having children.
noVoidTypeReturn	Disallow returning a value from a function with the return type ‘void’
useExhaustiveDependencies	Enforce correct dependency usage within React hooks.
useHookAtTopLevel	Enforce that all React hooks are being called from the Top Level component functions.
useImageSize	Enforces that <img> elements have both width and height attributes.
useImportExtensions	Enforce file extensions for relative imports.
useIsNan	Require calls to isNaN() when checking for NaN.
useJsonImportAttributes	Enforces the use of with { type: "json" } for JSON module imports.
useJsxKeyInIterable	Disallow missing key props in iterators/collection literals.
useParseIntRadix	Enforce the consistent use of the radix argument when using parseInt().
useQwikClasslist	Prefer using the class prop as a classlist over the classnames helper.
useSingleJsDocAsterisk	Enforce JSDoc comment lines to start with a single asterisk, except for the first one.
useUniqueElementIds	Prevent the usage of static string literal id attribute on elements.
useValidForDirection	Enforce “for” loop update clause moving the counter in the right direction.
useValidTypeof	This rule checks that the result of a typeof expression is compared to a valid value.
useYield	Require generator functions to contain yield.

Rule name	Description	Properties
noAmbiguousAnchorText	Disallow ambiguous anchor descriptions.
noBeforeInteractiveScriptOutsideDocument	Prevent usage of next/script’s beforeInteractive strategy outside of pages/_document.js in a Next.js project.
noContinue	Disallow continue statements.
noDeprecatedImports	Restrict imports of deprecated exports.
noDuplicateEnumValues	Disallow duplicate enum member values.
noDuplicatedSpreadProps	Disallow JSX prop spreading the same identifier multiple times.
noEmptySource	Disallow empty sources.
noEqualsToNull	Require the use of === or !== for comparison with null.
noExcessiveLinesPerFile	Restrict the number of lines in a file.
noFloatingPromises	Require Promise-like statements to be handled appropriately.
noForIn	Disallow iterating using a for-in loop.
noImportCycles	Prevent import cycles.
noIncrementDecrement	Disallows the usage of the unary operators ++ and —.
noJsxLiterals	Disallow string literals inside JSX elements.
noJsxPropsBind	Disallow .bind(), arrow functions, or function expressions in JSX props
noLeakedRender	Prevent problematic leaked values from being rendered.
noMisusedPromises	Disallow Promises to be used in places where they are almost certainly a
noMultiAssign	Disallow use of chained assignment expressions
noMultiStr	Disallow creating multiline strings by escaping newlines.
noNextAsyncClientComponent	Prevent client components from being async functions.
noParametersOnlyUsedInRecursion	Disallow function parameters that are only used in recursive calls.
noProto	Disallow the use of the deprecated __proto__ object property.
noReactForwardRef	Replaces usages of forwardRef with passing ref as a prop.
noReturnAssign	Disallow assignments in return statements.
noScriptUrl	Disallow javascript: URLs.
noShadow	Disallow variable declarations from shadowing variables declared in the outer scope.
noSyncScripts	Prevent the usage of synchronous scripts.
noTernary	Disallow ternary operators.
noUndeclaredEnvVars	Disallow the use of undeclared environment variables.
noUnknownAttribute	Disallow unknown DOM properties.
noUnnecessaryConditions	Disallow unnecessary type-based conditions that can be statically determined as redundant.
noUnresolvedImports	Warn when importing non-existing exports.
noUnusedExpressions	Disallow expression statements that are neither a function call nor an
noUselessCatchBinding	Disallow unused catch bindings.
noUselessUndefined	Disallow the use of useless undefined.
noVueDataObjectDeclaration	Enforce that Vue component data options are declared as functions.
noVueDuplicateKeys	Disallow duplicate keys in Vue component data, methods, computed properties, and other options.
noVueOptionsApi	Disallow the use of Vue Options API.
noVueReservedKeys	Disallow reserved keys in Vue component data and computed properties.
noVueReservedProps	Disallow reserved names to be used as props.
noVueSetupPropsReactivityLoss	Disallow destructuring of props passed to setup in Vue projects.
useArraySortCompare	Require Array#sort and Array#toSorted calls to always provide a compareFunction.
useAwaitThenable	Enforce that await is only used on Promise values.
useConsistentArrowReturn	Enforce consistent arrow function bodies.
useDestructuring	Require destructuring from arrays and/or objects
useErrorCause	Enforce that new Error() is thrown with the original error as cause.
useExhaustiveSwitchCases	Require switch-case statements to be exhaustive.
useExplicitType	Enforce types in functions, methods, variables, and parameters.
useFind	Enforce the use of Array.prototype.find() over Array.prototype.filter() followed by [0] when looking for a single result.
useMaxParams	Enforce a maximum number of parameters in function definitions.
useQwikMethodUsage	Disallow use* hooks outside of component$ or other use* hooks in Qwik applications.
useQwikValidLexicalScope	Disallow unserializable expressions in Qwik dollar ($) scopes.
useRegexpExec	Enforce RegExp#exec over String#match if no global flag is provided.
useSortedClasses	Enforce the sorting of CSS utility classes.
useSpread	Enforce the use of the spread operator over .apply().
useVueConsistentDefinePropsDeclaration	Enforce consistent defineProps declaration style.
useVueDefineMacrosOrder	Enforce specific order of Vue compiler macros.
useVueMultiWordComponentNames	Enforce multi-word component names in Vue components.

Rule name	Description	Properties
noAccumulatingSpread	Disallow the use of spread (...) syntax on accumulators.
noAwaitInLoops	Disallow await inside loops.
noBarrelFile	Disallow the use of barrel file.
noDelete	Disallow the use of the delete operator.
noDynamicNamespaceImportAccess	Disallow accessing namespace imports dynamically.
noImgElement	Prevent usage of <img> element in a Next.js project.
noNamespaceImport	Disallow the use of namespace imports.
noReExportAll	Avoid re-export all.
noUnwantedPolyfillio	Prevent duplicate polyfills from Polyfill.io.