Overview

@typescript-eslint/eslint-plugin includes over 100 rules that detect best practice violations, bugs, and/or stylistic issues specifically for TypeScript code. All of our rules are listed below.

tip

Instead of enabling rules one by one, we recommend using one of our pre-defined configs to enable a large set of recommended rules.

Rules

The rules are listed in alphabetical order. You can optionally filter them based on these categories:

Config Group (⚙️)

Metadata

(These categories are explained in more detail below.)

Rule	⚙️	🔧	💭	🧱	💀
@typescript-eslint/adjacent-overload-signatures Require that function overload signatures be consecutive	🎨
@typescript-eslint/array-type Require consistently using either T[] or Array<T> for arrays	🎨	🔧
@typescript-eslint/await-thenable Disallow awaiting a value that is not a Thenable	✅	💡	💭
@typescript-eslint/ban-ts-comment Disallow @ts-<directive> comments or require descriptions after directives	✅	💡
@typescript-eslint/ban-tslint-comment Disallow // tslint:<rule-flag> comments	🎨	🔧
@typescript-eslint/class-literal-property-style Enforce that literals on classes are exposed in a consistent style	🎨	💡
@typescript-eslint/class-methods-use-this Enforce that class methods utilize this				🧱
@typescript-eslint/consistent-generic-constructors Enforce specifying generic type arguments on type annotation or constructor name of a constructor call	🎨	🔧
@typescript-eslint/consistent-indexed-object-style Require or disallow the Record type	🎨	🔧 💡
@typescript-eslint/consistent-return Require return statements to either always or never specify values			💭	🧱
@typescript-eslint/consistent-type-assertions Enforce consistent usage of type assertions	🎨	🔧 💡
@typescript-eslint/consistent-type-definitions Enforce type definitions to consistently use either interface or type	🎨	🔧
@typescript-eslint/consistent-type-exports Enforce consistent usage of type exports		🔧	💭
@typescript-eslint/consistent-type-imports Enforce consistent usage of type imports		🔧
@typescript-eslint/default-param-last❄️ Enforce default parameters to be last				🧱
@typescript-eslint/dot-notation❄️ Enforce dot notation whenever possible	🎨	🔧	💭	🧱
@typescript-eslint/explicit-function-return-type Require explicit return types on functions and class methods
@typescript-eslint/explicit-member-accessibility Require explicit accessibility modifiers on class properties and methods		🔧 💡
@typescript-eslint/explicit-module-boundary-types Require explicit return and argument types on exported functions' and classes' public class methods
@typescript-eslint/init-declarations❄️ Require or disallow initialization in variable declarations				🧱
@typescript-eslint/max-params Enforce a maximum number of parameters in function definitions				🧱
@typescript-eslint/member-ordering❄️ Require a consistent member declaration order
@typescript-eslint/method-signature-style Enforce using a particular method signature syntax		🔧
@typescript-eslint/naming-convention❄️ Enforce naming conventions for everything across a codebase			💭
@typescript-eslint/no-array-constructor Disallow generic Array constructors	✅	🔧		🧱
@typescript-eslint/no-array-delete Disallow using the delete operator on array values	✅	💡	💭
@typescript-eslint/no-base-to-string Require .toString() and .toLocaleString() to only be called on objects which provide useful information when stringified	✅		💭
@typescript-eslint/no-confusing-non-null-assertion Disallow non-null assertion in locations that may be confusing	🎨	💡
@typescript-eslint/no-confusing-void-expression Require expressions of type void to appear in statement position	🔒	🔧 💡	💭
@typescript-eslint/no-deprecated Disallow using code marked as @deprecated	🔒		💭
@typescript-eslint/no-dupe-class-members Disallow duplicate class members				🧱
@typescript-eslint/no-duplicate-enum-values Disallow duplicate enum member values	✅
@typescript-eslint/no-duplicate-type-constituents Disallow duplicate constituents of union or intersection types	✅	🔧	💭
@typescript-eslint/no-dynamic-delete Disallow using the delete operator on computed key expressions	🔒	🔧
@typescript-eslint/no-empty-function Disallow empty functions	🎨			🧱
@typescript-eslint/no-empty-interface Disallow the declaration of empty interfaces		🔧 💡			💀
@typescript-eslint/no-empty-object-type Disallow accidentally using the "empty object" type	✅	💡
@typescript-eslint/no-explicit-any Disallow the any type	✅	🔧 💡
@typescript-eslint/no-extra-non-null-assertion Disallow extra non-null assertions	✅	🔧
@typescript-eslint/no-extraneous-class Disallow classes used as namespaces	🔒
@typescript-eslint/no-floating-promises Require Promise-like statements to be handled appropriately	✅	💡	💭
@typescript-eslint/no-for-in-array Disallow iterating over an array with a for-in loop	✅		💭
@typescript-eslint/no-implied-eval Disallow the use of eval()-like functions	✅		💭	🧱
@typescript-eslint/no-import-type-side-effects Enforce the use of top-level import type qualifier when an import only has specifiers with inline type qualifiers		🔧
@typescript-eslint/no-inferrable-types Disallow explicit type declarations for variables or parameters initialized to a number, string, or boolean	🎨	🔧
@typescript-eslint/no-invalid-this Disallow this keywords outside of classes or class-like objects				🧱
@typescript-eslint/no-invalid-void-type Disallow void type outside of generic or return types	🔒
@typescript-eslint/no-loop-func Disallow function declarations that contain unsafe references inside loop statements				🧱
@typescript-eslint/no-loss-of-precision Disallow literal numbers that lose precision				🧱	💀
@typescript-eslint/no-magic-numbers❄️ Disallow magic numbers				🧱
@typescript-eslint/no-meaningless-void-operator Disallow the void operator except when used to discard a value	🔒	🔧 💡	💭
@typescript-eslint/no-misused-new Enforce valid definition of new and constructor	✅
@typescript-eslint/no-misused-promises Disallow Promises in places not designed to handle them	✅		💭
@typescript-eslint/no-misused-spread Disallow using the spread operator when it might cause unexpected behavior	🔒	💡	💭
@typescript-eslint/no-mixed-enums Disallow enums from having both number and string members	🔒		💭
@typescript-eslint/no-namespace Disallow TypeScript namespaces	✅
@typescript-eslint/no-non-null-asserted-nullish-coalescing Disallow non-null assertions in the left operand of a nullish coalescing operator	🔒	💡
@typescript-eslint/no-non-null-asserted-optional-chain Disallow non-null assertions after an optional chain expression	✅	💡
@typescript-eslint/no-non-null-assertion Disallow non-null assertions using the ! postfix operator	🔒	💡
@typescript-eslint/no-redeclare Disallow variable redeclaration				🧱
@typescript-eslint/no-redundant-type-constituents Disallow members of unions and intersections that do nothing or override type information	✅		💭
@typescript-eslint/no-require-imports Disallow invocation of require()	✅
@typescript-eslint/no-restricted-imports Disallow specified modules when loaded by import				🧱
@typescript-eslint/no-restricted-types Disallow certain types		🔧 💡
@typescript-eslint/no-shadow Disallow variable declarations from shadowing variables declared in the outer scope				🧱
@typescript-eslint/no-this-alias Disallow aliasing this	✅
@typescript-eslint/no-type-alias Disallow type aliases					💀
@typescript-eslint/no-unnecessary-boolean-literal-compare Disallow unnecessary equality comparisons against boolean literals	🔒	🔧	💭
@typescript-eslint/no-unnecessary-condition Disallow conditionals where the type is always truthy or always falsy	🔒	💡	💭
@typescript-eslint/no-unnecessary-parameter-property-assignment Disallow unnecessary assignment of constructor property parameter
@typescript-eslint/no-unnecessary-qualifier Disallow unnecessary namespace qualifiers		🔧	💭
@typescript-eslint/no-unnecessary-template-expression Disallow unnecessary template expressions	🔒	🔧	💭
@typescript-eslint/no-unnecessary-type-arguments Disallow type arguments that are equal to the default	🔒	🔧	💭
@typescript-eslint/no-unnecessary-type-assertion Disallow type assertions that do not change the type of an expression	✅	🔧	💭
@typescript-eslint/no-unnecessary-type-constraint Disallow unnecessary constraints on generic types	✅	💡
@typescript-eslint/no-unnecessary-type-conversion Disallow conversion idioms when they do not change the type or value of the expression	🔒	💡	💭
@typescript-eslint/no-unnecessary-type-parameters Disallow type parameters that aren't used multiple times	🔒	💡	💭
@typescript-eslint/no-unsafe-argument Disallow calling a function with a value with type any	✅		💭
@typescript-eslint/no-unsafe-assignment Disallow assigning a value with type any to variables and properties	✅		💭
@typescript-eslint/no-unsafe-call Disallow calling a value with type any	✅		💭
@typescript-eslint/no-unsafe-declaration-merging Disallow unsafe declaration merging	✅
@typescript-eslint/no-unsafe-enum-comparison Disallow comparing an enum value with a non-enum value	✅	💡	💭
@typescript-eslint/no-unsafe-function-type Disallow using the unsafe built-in Function type	✅
@typescript-eslint/no-unsafe-member-access Disallow member access on a value with type any	✅		💭
@typescript-eslint/no-unsafe-return Disallow returning a value with type any from a function	✅		💭
@typescript-eslint/no-unsafe-type-assertion Disallow type assertions that narrow a type			💭
@typescript-eslint/no-unsafe-unary-minus Require unary negation to take a number	✅		💭
@typescript-eslint/no-unused-expressions Disallow unused expressions	✅			🧱
@typescript-eslint/no-unused-vars Disallow unused variables	✅			🧱
@typescript-eslint/no-use-before-define Disallow the use of variables before they are defined				🧱
@typescript-eslint/no-useless-constructor Disallow unnecessary constructors	🔒	💡		🧱
@typescript-eslint/no-useless-empty-export Disallow empty exports that don't change anything in a module file		🔧
@typescript-eslint/no-var-requires Disallow require statements except in import statements					💀
@typescript-eslint/no-wrapper-object-types Disallow using confusing built-in primitive class wrappers	✅	🔧
@typescript-eslint/non-nullable-type-assertion-style Enforce non-null assertions over explicit type assertions	🎨	🔧	💭
@typescript-eslint/only-throw-error Disallow throwing non-Error values as exceptions	✅		💭	🧱
@typescript-eslint/parameter-properties Require or disallow parameter properties in class constructors
@typescript-eslint/prefer-as-const Enforce the use of as const over literal type	✅	🔧 💡
@typescript-eslint/prefer-destructuring❄️ Require destructuring from arrays and/or objects		🔧	💭	🧱
@typescript-eslint/prefer-enum-initializers Require each enum member value to be explicitly initialized		💡
@typescript-eslint/prefer-find Enforce the use of Array.prototype.find() over Array.prototype.filter() followed by [0] when looking for a single result	🎨	💡	💭
@typescript-eslint/prefer-for-of Enforce the use of for-of loop over the standard for loop where possible	🎨
@typescript-eslint/prefer-function-type Enforce using function types instead of interfaces with call signatures	🎨	🔧
@typescript-eslint/prefer-includes Enforce includes method over indexOf method	🎨	🔧	💭
@typescript-eslint/prefer-literal-enum-member Require all enum members to be literal values	🔒
@typescript-eslint/prefer-namespace-keyword Require using namespace keyword over module keyword to declare custom TypeScript modules	✅	🔧
@typescript-eslint/prefer-nullish-coalescing Enforce using the nullish coalescing operator instead of logical assignments or chaining	🎨	💡	💭
@typescript-eslint/prefer-optional-chain Enforce using concise optional chain expressions instead of chained logical ands, negated logical ors, or empty objects	🎨	🔧 💡	💭
@typescript-eslint/prefer-promise-reject-errors Require using Error objects as Promise rejection reasons	✅		💭	🧱
@typescript-eslint/prefer-readonly Require private members to be marked as readonly if they're never modified outside of the constructor		🔧	💭
@typescript-eslint/prefer-readonly-parameter-types Require function parameters to be typed as readonly to prevent accidental mutation of inputs			💭
@typescript-eslint/prefer-reduce-type-parameter Enforce using type parameter when calling Array#reduce instead of using a type assertion	🔒	🔧	💭
@typescript-eslint/prefer-regexp-exec Enforce RegExp#exec over String#match if no global flag is provided	🎨	🔧	💭
@typescript-eslint/prefer-return-this-type Enforce that this is used when only this type is returned	🔒	🔧	💭
@typescript-eslint/prefer-string-starts-ends-with Enforce using String#startsWith and String#endsWith over other equivalent methods of checking substrings	🎨	🔧	💭
@typescript-eslint/prefer-ts-expect-error Enforce using @ts-expect-error over @ts-ignore		🔧			💀
@typescript-eslint/promise-function-async Require any function or method that returns a Promise to be marked async		🔧	💭
@typescript-eslint/related-getter-setter-pairs Enforce that get() types should be assignable to their equivalent set() type	🔒		💭
@typescript-eslint/require-array-sort-compare Require Array#sort and Array#toSorted calls to always provide a compareFunction			💭
@typescript-eslint/require-await Disallow async functions which do not return promises and have no await expression	✅	💡	💭	🧱
@typescript-eslint/restrict-plus-operands Require both operands of addition to be the same type and be bigint, number, or string	✅		💭
@typescript-eslint/restrict-template-expressions Enforce template literal expressions to be of string type	✅		💭
@typescript-eslint/return-await Enforce consistent awaiting of returned promises	🔒	🔧 💡	💭
@typescript-eslint/sort-type-constituents Enforce constituents of a type union/intersection to be sorted alphabetically		🔧 💡			💀
@typescript-eslint/strict-boolean-expressions Disallow certain types in boolean expressions		💡	💭
@typescript-eslint/switch-exhaustiveness-check Require switch-case statements to be exhaustive		💡	💭
@typescript-eslint/triple-slash-reference Disallow certain triple slash directives in favor of ES6-style import declarations	✅
@typescript-eslint/typedef Require type annotations in certain places					💀
@typescript-eslint/unbound-method Enforce unbound methods are called with their expected scope	✅		💭
@typescript-eslint/unified-signatures Disallow two overloads that could be unified into one with a union or an optional/rest parameter	🔒
@typescript-eslint/use-unknown-in-catch-callback-variable Enforce typing arguments in Promise rejection callbacks as unknown	🔒	💡	💭

Filtering

Config Group (⚙️)

"Config Group" refers to the pre-defined config that includes the rule. Extending from a configuration preset allow for enabling a large set of recommended rules all at once.

Metadata

• 🔧 fixable refers to whether the rule contains an ESLint --fix auto-fixer.
• 💡 has suggestions refers to whether the rule contains an ESLint suggestion fixer.
  • Sometimes, it is not safe to automatically fix the code with an auto-fixer. But in these cases, we often have a good guess of what the correct fix should be, and we can provide it as a suggestion to the developer.
• 💭 requires type information refers to whether the rule requires typed linting.
• 🧱 extension rule means that the rule is an extension of an core ESLint rule (see Extension Rules).
• 💀 deprecated rule means that the rule should no longer be used and will be removed from the plugin in a future version.

Extension Rules

Some core ESLint rules do not support TypeScript syntax: either they crash, ignore the syntax, or falsely report against it. In these cases, we create what we call an "extension rule": a rule within our plugin that has the same functionality, but also supports TypeScript.

Extension rules generally completely replace the base rule from ESLint core. If the base rule is enabled in a config you extend from, you'll need to disable the base rule:

module.exports = {
  extends: ['eslint:recommended'],
  rules: {
    // Note: you must disable the base rule as it can report incorrect errors
    'no-unused-vars': 'off',
    '@typescript-eslint/no-unused-vars': 'error',
  },
};

Search for 🧱 extension rules in this page to see all extension rules.

Frozen Rules

When rules are feature complete, they are marked as frozen (indicated with ❄️ in the documentation). This applies to standalone rules that are complete, as well as extension rules whose underlying core ESLint rules are frozen. After that point, we expect users to use disable comments when they find an edge case that isn’t covered.

When a rule is frozen, it means:

• Bug fixes: We will still fix confirmed bugs.
• New ECMAScript features: We will ensure compatibility with new ECMAScript features, meaning the rule will not break on new syntax.
• TypeScript support: We will ensure compatibility with TypeScript syntax, meaning the rule will not break on TypeScript syntax and violations are appropriate for TypeScript.
• New options: We will not add any new options unless an option is the only way to fix a bug or support a newly-added ECMAScript feature.

If you find that a frozen rule would work better for you with a change, we recommend copying the rule source code and modifying it to fit your needs.