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JavaScript Rules

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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.

a11y

Section titled “a11y”

| 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. | |

complexity

Section titled “complexity”

| 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. | | | noUselessCatchBinding | Disallow unused catch bindings. | | | 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. | | | noUselessUndefined | Disallow the use of useless undefined. | | | 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. | | | useMaxParams | Enforce a maximum number of parameters in function definitions. | | | 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. | |

correctness

Section titled “correctness”

| 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. | | | noNextAsyncClientComponent | Prevent client components from being async functions. | | | 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 | | | noUnresolvedImports | Warn when importing non-existing exports. | | | 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’ | | | 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. | | | 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. | | | 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. | | | useQwikMethodUsage | Disallow use* hooks outside of component$ or other use* hooks in Qwik applications. | | | useQwikValidLexicalScope | Disallow unserializable expressions in Qwik dollar ($) scopes. | | | 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. | |

nursery

Section titled “nursery”

| Rule name | Description | Properties | | --- | --- | --- | | noAmbiguousAnchorText | Disallow ambiguous anchor descriptions. | | | noBaseToString | Require stringification to avoid values that only use the default object representation. | | | noBeforeInteractiveScriptOutsideDocument | Prevent usage of next/script’s beforeInteractive strategy outside of pages/_document.js in a Next.js project. | | | noComponentHookFactories | Disallows defining React components or custom hooks inside other functions. | | | noConditionalExpect | Disallow conditional expect() calls inside tests. | | | noContinue | Disallow continue statements. | | | noDivRegex | Disallow equal signs explicitly at the beginning of regular expressions. | | | noDrizzleDeleteWithoutWhere | Require .where() to be called when using .delete() with Drizzle ORM. | | | noDrizzleUpdateWithoutWhere | Require .where() to be called when using .update() with Drizzle ORM. | | | noDuplicateEnumValues | Disallow duplicate enum member values. | | | noDuplicatedSpreadProps | Disallow JSX prop spreading the same identifier multiple times. | | | noEqualsToNull | Require the use of === or !== for comparison with null. | | | noExcessiveClassesPerFile | Enforce a maximum number of classes per file. | | | noExcessiveLinesPerFile | Restrict the number of lines in a file. | | | noExcessiveNestedCallbacks | Enforce a maximum depth that callbacks can be nested. | | | noFloatingClasses | Disallow new operators outside of assignments or comparisons. | | | noFloatingPromises | Require Promise-like statements to be handled appropriately. | | | noForIn | Disallow iterating using a for-in loop. | | | noIdenticalTestTitle | Disallow identical titles in test suites and test cases. | | | noImpliedEval | Disallow the use of eval()-like methods. | | | noIncrementDecrement | Disallows the usage of the unary operators ++ and —. | | | noInlineStyles | Disallow the use of inline styles. | | | noJsxLeakedDollar | Flags text nodes with a trailing $ before a JSX expression. | | | noJsxNamespace | Disallow JSX namespace syntax. | | | noJsxPropsBind | Disallow .bind(), arrow functions, or function expressions in JSX props | | | noLeakedRender | Prevent problematic leaked values from being rendered. | | | noLoopFunc | Disallow functions declared inside loops that capture unsafe outer variables. | | | noMisleadingReturnType | Detect return type annotations that are misleadingly wider than what | | | 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. | | | noNestedPromises | Disallow nested .then() or .catch() promise calls. | | | noParametersOnlyUsedInRecursion | Disallow function parameters that are only used in recursive calls. | | | noPlaywrightElementHandle | Disallow usage of element handles (page.$() and page.$$()). | | | noPlaywrightEval | Disallow usage of page.$eval() and page.$$eval(). | | | noPlaywrightForceOption | Disallow usage of the { force: true } option. | | | noPlaywrightMissingAwait | Enforce Playwright async APIs to be awaited or returned. | | | noPlaywrightNetworkidle | Disallow usage of the networkidle option. | | | noPlaywrightPagePause | Disallow using page.pause(). | | | noPlaywrightUselessAwait | Disallow unnecessary await for Playwright methods that don’t return promises. | | | noPlaywrightWaitForNavigation | Disallow using page.waitForNavigation(). | | | noPlaywrightWaitForSelector | Disallow using page.waitForSelector(). | | | noPlaywrightWaitForTimeout | Disallow using page.waitForTimeout(). | | | noProto | Disallow the use of the deprecated __proto__ object property. | | | noReactNativeDeepImports | Disallow deep imports from the react-native package. | | | noReactNativeLiteralColors | Disallow color literals in React Native styles. | | | noReactNativeRawText | Disallow raw text outside <Text> components in React Native. | | | noReactStringRefs | Disallow string refs in React components. | | | noRedundantDefaultExport | Checks if a default export exports the same symbol as a named export. | | | 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 conditions that always evaluate to the same value. | | | noUnnecessaryTemplateExpression | Disallow unnecessary template expressions. | | | noUnsafePlusOperands | Disallow + operations with operands that are known to be unsafe. | | | noUselessReturn | Disallow redundant return statements. | | | noUselessTypeConversion | Disallow type conversions that do not change the type of an expression. | | | noVueArrowFuncInWatch | Disallows using arrow functions when defining a watcher. | | | noVueImportCompilerMacros | Disallow importing Vue compiler macros. | | | noVueOptionsApi | Disallow the use of Vue Options API. | | | noVueRefAsOperand | Disallow the use of value wrapped by ref()(Composition API) as operand | | | useArraySome | Prefer Array.prototype.some() over verbose existence checks. | | | useArraySortCompare | Require Array#sort and Array#toSorted calls to always provide a compareFunction. | | | useAwaitThenable | Enforce that await is only used on Promise values. | | | useConsistentEnumValueType | Disallow enums from having both number and string members. | | | useConsistentMethodSignatures | Enforce consistent use of either method signatures or function properties within interfaces and type aliases. | | | useConsistentTestIt | Enforce consistent use of it or test for test functions. | | | useDestructuring | Require destructuring from arrays and/or objects | | | useDisposables | Detects a disposable object assigned to a variable without using or await using syntax. | | | useDomNodeTextContent | Prefer .textContent over .innerText for DOM node text. | | | useDomQuerySelector | Prefer querySelector() and querySelectorAll() over older DOM query APIs. | | | useErrorCause | Enforce that new Error() is thrown with the original error as cause. | | | useExhaustiveSwitchCases | Require switch-case statements to be exhaustive. | | | useExpect | Ensure that test functions contain at least one expect() or similar assertion. | | | useExplicitReturnType | Require explicit return types on functions and class methods. | | | 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. | | | useGlobalThis | Enforce the use of globalThis over window, self, and global. | | | useIframeSandbox | Enforce the ‘sandbox’ attribute for ‘iframe’ elements. | | | useImportsFirst | Enforce that all imports appear at the top of the module. | | | useInlineScriptId | Enforce id attribute on next/script components with inline content or dangerouslySetInnerHTML. | | | useMathMinMax | Prefer Math.min() and Math.max() over ternaries for simple comparisons. | | | useNamedCaptureGroup | Enforce using named capture groups in regular expression. | | | useNullishCoalescing | Enforce using the nullish coalescing operator (??) instead of logical or (||). | | | usePlaywrightValidDescribeCallback | Enforce valid describe() callback. | | | useQwikLoaderLocation | Enforce that Qwik loader functions are declared in the correct location. | | | useReactAsyncServerFunction | Require functions with the “use server” directive to be async. | | | useReactNativePlatformComponents | Ensure that platform-specific React Native components are only | | | useReduceTypeParameter | Enforce using a type parameter on Array#reduce instead of casting the initial value. | | | useRegexpExec | Enforce RegExp#exec over String#match if no global flag is provided. | | | useRegexpTest | Enforce the use of RegExp.prototype.test() over String.prototype.match() and RegExp.prototype.exec() in boolean contexts. | | | useSortedClasses | Enforce the sorting of CSS utility classes. | | | useSpread | Enforce the use of the spread operator over .apply(). | | | useStringStartsEndsWith | Prefer String#startsWith() and String#endsWith() over verbose prefix and suffix checks. | | | useTestHooksInOrder | Enforce that test lifecycle hooks are declared in the order they execute. | | | useTestHooksOnTop | Enforce that lifecycle hooks appear before any test cases in the same block. | | | useThisInClassMethods | Enforce that class methods utilize this. | | | useUnicodeRegex | Enforce the use of the u or v flag for regular expressions. | | | useVarsOnTop | Require var declarations to appear at the top of their containing scope. | | | useVueConsistentDefinePropsDeclaration | Enforce consistent defineProps declaration style. | | | useVueDefineMacrosOrder | Enforce specific order of Vue compiler macros. | | | useVueMultiWordComponentNames | Enforce multi-word component names in Vue components. | | | useVueNextTickPromise | Enforces Promise syntax when using Vue nextTick. | |

performance

Section titled “performance”

| 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. | | | useGoogleFontPreconnect | Ensure the preconnect attribute is used when using Google Fonts. | | | useSolidForComponent | Enforce using Solid’s <For /> component for mapping an array to JSX elements. | | | useTopLevelRegex | Require regex literals to be declared at the top level. | |

security

Section titled “security”

| Rule name | Description | Properties | | --- | --- | --- | | noBlankTarget | Disallow target="_blank" attribute without rel="noopener". | | | noDangerouslySetInnerHtml | Prevent the usage of dangerous JSX props | | | noDangerouslySetInnerHtmlWithChildren | Report when a DOM element or a component uses both children and dangerouslySetInnerHTML prop. | | | noGlobalEval | Disallow the use of global eval(). | | | noSecrets | Disallow usage of sensitive data such as API keys and tokens. | |

style

Section titled “style”

| Rule name | Description | Properties | | --- | --- | --- | | noCommonJs | Disallow use of CommonJs module system in favor of ESM style imports. | | | noDefaultExport | Disallow default exports. | | | noDoneCallback | Disallow using a callback in asynchronous tests and hooks. | | | noEnum | Disallow TypeScript enum. | | | noExportedImports | Disallow exporting an imported variable. | | | noHeadElement | Prevent usage of <head> element in a Next.js project. | | | noImplicitBoolean | Disallow implicit true values on JSX boolean attributes | | | noInferrableTypes | Disallow type annotations for variables, parameters, and class properties initialized with a literal expression. | | | noJsxLiterals | Disallow string literals inside JSX elements. | | | noMagicNumbers | Reports usage of “magic numbers” — numbers used directly instead of being assigned to named constants. | | | noNamespace | Disallow the use of TypeScript’s namespaces. | | | noNegationElse | Disallow negation in the condition of an if statement if it has an else clause. | | | noNestedTernary | Disallow nested ternary expressions. | | | noNonNullAssertion | Disallow non-null assertions using the ! postfix operator. | | | noParameterAssign | Disallow reassigning function parameters. | | | noParameterProperties | Disallow the use of parameter properties in class constructors. | | | noProcessEnv | Disallow the use of process.env. | | | noRestrictedGlobals | This rule allows you to specify global variable names that you don’t want to use in your application. | | | noRestrictedImports | Disallow specified modules when loaded by import or require. | | | noRestrictedTypes | Disallow user defined types. | | | noShoutyConstants | Disallow the use of constants which its value is the upper-case version of its name. | | | noSubstr | Enforce the use of String.slice() over String.substr() and String.substring(). | | | noUnusedTemplateLiteral | Disallow template literals if interpolation and special-character handling are not needed | | | noUselessElse | Disallow else block when the if block breaks early. | | | noYodaExpression | Disallow the use of yoda expressions. | | | useArrayLiterals | Disallow Array constructors. | | | useAsConstAssertion | Enforce the use of as const over literal type and type annotation. | | | useAtIndex | Use at() instead of integer index access. | | | useBlockStatements | Requires following curly brace conventions. | | | useCollapsedElseIf | Enforce using else if instead of nested if in else clauses. | | | useCollapsedIf | Enforce using single if instead of nested if clauses. | | | useComponentExportOnlyModules | Enforce declaring components only within modules that export React Components exclusively. | | | useConsistentArrayType | Require consistently using either T[] or Array<T> | | | useConsistentArrowReturn | Enforce consistent arrow function bodies. | | | useConsistentBuiltinInstantiation | Enforce the use of new for all builtins, except String, Number and Boolean. | | | useConsistentCurlyBraces | This rule enforces consistent use of curly braces inside JSX attributes and JSX children. | | | useConsistentMemberAccessibility | Require consistent accessibility modifiers on class properties and methods. | | | useConsistentObjectDefinitions | Require the consistent declaration of object literals. | | | useConsistentTypeDefinitions | Enforce type definitions to consistently use either interface or type. | | | useConst | Require const declarations for variables that are only assigned once. | | | useDefaultParameterLast | Enforce default function parameters and optional function parameters to be last. | | | useDefaultSwitchClause | Require the default clause in switch statements. | | | useEnumInitializers | Require that each enum member value be explicitly initialized. | | | useExplicitLengthCheck | Enforce explicitly comparing the length, size, byteLength or byteOffset property of a value. | | | useExponentiationOperator | Disallow the use of Math.pow in favor of the ** operator. | | | useExportType | Promotes the use of export type for types. | | | useExportsLast | Require that all exports are declared after all non-export statements. | | | useFilenamingConvention | Enforce naming conventions for JavaScript and TypeScript filenames. | | | useForOf | Prefer using for...of loops over standard for loops where possible. | | | useFragmentSyntax | This rule enforces the use of <>...</> over <Fragment>...</Fragment>. | | | useGroupedAccessorPairs | Enforce that getters and setters for the same property are adjacent in class and object definitions. | | | useImportType | Promotes the use of import type for types. | | | useLiteralEnumMembers | Require all enum members to be literal values. | | | useNamingConvention | Enforce naming conventions for everything across a codebase. | | | useNodeAssertStrict | Promotes the usage of node:assert/strict over node:assert. | | | useNodejsImportProtocol | Enforces using the node: protocol for Node.js builtin modules. | | | useNumberNamespace | Use the Number properties instead of global ones. | | | useNumericSeparators | Enforce the use of numeric separators in numeric literals. | | | useObjectSpread | Prefer object spread over Object.assign() when constructing new objects. | | | useReactFunctionComponents | Enforce that components are defined as functions and never as classes. | | | useReadonlyClassProperties | Enforce marking members as readonly if they are never modified outside the constructor. | | | useSelfClosingElements | Prevent extra closing tags for components without children. | | | useShorthandAssign | Require assignment operator shorthand where possible. | | | useShorthandFunctionType | Enforce using function types instead of object type with call signatures. | | | useSingleVarDeclarator | Disallow multiple variable declarations in the same variable statement | | | useSymbolDescription | Require a description parameter for the Symbol(). | | | useTemplate | Prefer template literals over string concatenation. | | | useThrowNewError | Require new when throwing an error. | | | useThrowOnlyError | Disallow throwing non-Error values. | | | useTrimStartEnd | Enforce the use of String.trimStart() and String.trimEnd() over String.trimLeft() and String.trimRight(). | | | useUnifiedTypeSignatures | Disallow overload signatures that can be unified into a single signature. | |

suspicious

Section titled “suspicious”

| Rule name | Description | Properties | | --- | --- | --- | | noAlert | Disallow the use of alert, confirm, and prompt. | | | noApproximativeNumericConstant | Use standard constants instead of approximated literals. | | | noArrayIndexKey | Discourage the usage of Array index in keys. | | | noAssignInExpressions | Disallow assignments in expressions. | | | noAsyncPromiseExecutor | Disallows using an async function as a Promise executor. | | | noBitwiseOperators | Disallow bitwise operators. | | | noCatchAssign | Disallow reassigning exceptions in catch clauses. | | | noClassAssign | Disallow reassigning class members. | | | noCommentText | Prevent comments from being inserted as text nodes | | | noCompareNegZero | Disallow comparing against -0 | | | noConfusingLabels | Disallow labeled statements that are not loops. | | | noConfusingVoidType | Disallow void type outside of generic or return types. | | | noConsole | Disallow the use of console. | | | noConstEnum | Disallow TypeScript const enum | | | noConstantBinaryExpressions | Disallow expressions where the operation doesn’t affect the value | | | noControlCharactersInRegex | Prevents from having control characters and some escape sequences that match control characters in regular expression literals. | | | noDebugger | Disallow the use of debugger | | | noDeprecatedImports | Restrict imports of deprecated exports. | | | noDocumentCookie | Disallow direct assignments to document.cookie. | | | noDocumentImportInPage | Prevents importing next/document outside of pages/_document.jsx in Next.js projects. | | | noDoubleEquals | Require the use of === and !==. | | | noDuplicateCase | Disallow duplicate case labels. | | | noDuplicateClassMembers | Disallow duplicate class members. | | | noDuplicateElseIf | Disallow duplicate conditions in if-else-if chains | | | noDuplicateJsxProps | Prevents JSX properties to be assigned multiple times. | | | noDuplicateObjectKeys | Disallow two keys with the same name inside objects. | | | noDuplicateParameters | Disallow duplicate function parameter name. | | | noDuplicateTestHooks | A describe block should not contain duplicate hooks. | | | noEmptyBlockStatements | Disallow empty block statements and static blocks. | | | noEmptyInterface | Disallow the declaration of empty interfaces. | | | noEmptySource | Disallow empty sources. | | | noEvolvingTypes | Disallow variables from evolving into any type through reassignments. | | | noExplicitAny | Disallow the any type usage. | | | noExportsInTest | Disallow using export or module.exports in files containing tests | | | noExtraNonNullAssertion | Prevents the wrong usage of the non-null assertion operator (!) in TypeScript files. | | | noFallthroughSwitchClause | Disallow fallthrough of switch clauses. | | | noFocusedTests | Disallow focused tests. | | | noFunctionAssign | Disallow reassigning function declarations. | | | noGlobalAssign | Disallow assignments to native objects and read-only global variables. | | | noGlobalIsFinite | Use Number.isFinite instead of global isFinite. | | | noGlobalIsNan | Use Number.isNaN instead of global isNaN. | | | noHeadImportInDocument | Prevent using the next/head module in pages/_document.js on Next.js projects. | | | noImplicitAnyLet | Disallow use of implicit any type on variable declarations. | | | noImportAssign | Disallow assigning to imported bindings | | | noImportCycles | Prevent import cycles. | | | noIrregularWhitespace | Disallows the use of irregular whitespace characters. | | | noLabelVar | Disallow labels that share a name with a variable | | | noMisleadingCharacterClass | Disallow characters made with multiple code points in character class syntax. | | | noMisleadingInstantiator | Enforce proper usage of new and constructor. | | | noMisplacedAssertion | Checks that the assertion function, for example expect, is placed inside an it() function call. | | | noMisrefactoredShorthandAssign | Disallow shorthand assign when variable appears on both sides. | | | noNonNullAssertedOptionalChain | Disallow non-null assertions after optional chaining expressions. | | | noOctalEscape | Disallow octal escape sequences in string literals | | | noPrototypeBuiltins | Disallow direct use of Object.prototype builtins. | | | noReactForwardRef | Replaces usages of forwardRef with passing ref as a prop. | | | noReactSpecificProps | Prevents React-specific JSX properties from being used. | | | noRedeclare | Disallow variable, function, class, and type redeclarations in the same scope. | | | noRedundantUseStrict | Prevents from having redundant "use strict". | | | noSelfCompare | Disallow comparisons where both sides are exactly the same. | | | noShadowRestrictedNames | Disallow identifiers from shadowing restricted names. | | | noSkippedTests | Disallow disabled tests. | | | noSparseArray | Prevents the use of sparse arrays (arrays with holes). | | | noSuspiciousSemicolonInJsx | It detects possible “wrong” semicolons inside JSX elements. | | | noTemplateCurlyInString | Disallow template literal placeholder syntax in regular strings. | | | noThenProperty | Disallow then property. | | | noTsIgnore | Prevents the use of the TypeScript directive @ts-ignore. | | | noUnassignedVariables | Disallow let or var variables that are read but never assigned. | | | noUnsafeDeclarationMerging | Disallow unsafe declaration merging between interfaces and classes. | | | noUnsafeNegation | Disallow using unsafe negation. | | | noUnusedExpressions | Disallow expression statements that are neither a function call nor an | | | noUselessEscapeInString | Disallow unnecessary escapes in string literals. | | | noUselessRegexBackrefs | Disallow useless backreferences in regular expression literals that always match an empty string. | | | noVar | Disallow the use of var | | | noWith | Disallow with statements in non-strict contexts. | | | useAdjacentOverloadSignatures | Disallow the use of overload signatures that are not next to each other. | | | useAwait | Ensure async functions utilize await. | | | useDefaultSwitchClauseLast | Enforce default clauses in switch statements to be last | | | useErrorMessage | Enforce passing a message value when creating a built-in error. | | | useGetterReturn | Enforce get methods to always return a value. | | | useGoogleFontDisplay | Enforces the use of a recommended display strategy with Google Fonts. | | | useGuardForIn | Require for-in loops to include an if statement. | | | useIsArray | Use Array.isArray() instead of instanceof Array. | | | useIterableCallbackReturn | Enforce consistent return values in iterable callbacks. | | | useNamespaceKeyword | Require using the namespace keyword over the module keyword to declare TypeScript namespaces. | | | useNumberToFixedDigitsArgument | Enforce using the digits argument with Number#toFixed(). | | | useStaticResponseMethods | Use static Response methods instead of new Response() constructor when possible. | | | useStrictMode | Enforce the use of the directive "use strict" in script files. | |

Section titled “Recommended rules”

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