README.md

ESLint Plugin TypeScript

Getting Started

You can find our Getting Started docs here You can find our FAQ / Troubleshooting docs here

These docs walk you through setting up ESLint, this plugin, and our parser. If you know what you're doing and just want to quick start, read on...

Quick-start

Installation

Make sure you have TypeScript and @typescript-eslint/parser installed, then install the plugin:

yarn add -D @typescript-eslint/eslint-plugin

It is important that you use the same version number for @typescript-eslint/parser and @typescript-eslint/eslint-plugin.

Note: If you installed ESLint globally (using the -g flag) then you must also install @typescript-eslint/eslint-plugin globally.

Usage

Add @typescript-eslint/parser to the parser field and @typescript-eslint to the plugins section of your .eslintrc configuration file, then configure the rules you want to use under the rules section.

{
  "parser": "@typescript-eslint/parser",
  "plugins": ["@typescript-eslint"],
  "rules": {
    "@typescript-eslint/rule-name": "error"
  }
}

You can also enable all the recommended rules for our plugin. Add plugin:@typescript-eslint/recommended in extends:

{
  "extends": ["plugin:@typescript-eslint/recommended"]
}

Note: Make sure to use eslint --ext .js,.ts since by default eslint will only search for .js files.

Recommended Configs

You can also use eslint:recommended (the set of rules which are recommended for all projects by the ESLint Team) with this plugin. As noted in the root README, not all ESLint core rules are compatible with TypeScript, so you need to add both eslint:recommended and plugin:@typescript-eslint/eslint-recommended (which will adjust the one from ESLint appropriately for TypeScript) to your config:

{
  "extends": [
    "eslint:recommended",
    "plugin:@typescript-eslint/eslint-recommended",
    "plugin:@typescript-eslint/recommended"
  ]
}

As of version 2 of this plugin, by design, none of the rules in the main recommended config require type-checking in order to run. This means that they are more lightweight and faster to run.

Some highly valuable rules simply require type-checking in order to be implemented correctly, however, so we provide an additional config you can extend from called recommended-requiring-type-checking. You would apply this in addition to the recommended configs previously mentioned, e.g.:

{
  "extends": [
    "eslint:recommended",
    "plugin:@typescript-eslint/eslint-recommended",
    "plugin:@typescript-eslint/recommended",
    "plugin:@typescript-eslint/recommended-requiring-type-checking"
  ]
}

Pro Tip: For larger codebases you may want to consider splitting our linting into two separate stages: 1. fast feedback rules which operate purely based on syntax (no type-checking), 2. rules which are based on semantics (type-checking).

You can read more about linting with type information here

Supported Rules

Key: ✔️ = recommended, 🔧 = fixable, 💭 = requires type information

Name	Description	✔️	🔧	💭
@typescript-eslint/adjacent-overload-signatures	Require that member overloads be consecutive	✔️
@typescript-eslint/array-type	Requires using either T[] or Array<T> for arrays		🔧
@typescript-eslint/await-thenable	Disallows awaiting a value that is not a Thenable	✔️		💭
@typescript-eslint/ban-ts-ignore	Bans “// @ts-ignore” comments from being used	✔️
@typescript-eslint/ban-types	Bans specific types from being used	✔️	🔧
@typescript-eslint/brace-style	Enforce consistent brace style for blocks		🔧
@typescript-eslint/camelcase	Enforce camelCase naming convention	✔️
@typescript-eslint/class-name-casing	Require PascalCased class and interface names	✔️
@typescript-eslint/consistent-type-assertions	Enforces consistent usage of type assertions.	✔️
@typescript-eslint/consistent-type-definitions	Consistent with type definition either interface or type		🔧
@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/func-call-spacing	Require or disallow spacing between function identifiers and their invocations		🔧
@typescript-eslint/generic-type-naming	Enforces naming of generic type variables
@typescript-eslint/indent	Enforce consistent indentation		🔧
@typescript-eslint/interface-name-prefix	Require that interface names should or should not prefixed with I	✔️
@typescript-eslint/member-delimiter-style	Require a specific member delimiter style for interfaces and type literals	✔️	🔧
@typescript-eslint/member-naming	Enforces naming conventions for class members by visibility
@typescript-eslint/member-ordering	Require a consistent member declaration order
@typescript-eslint/no-array-constructor	Disallow generic Array constructors	✔️	🔧
@typescript-eslint/no-dynamic-delete	Bans usage of the delete operator with 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-explicit-any	Disallow usage of the any type	✔️	🔧
@typescript-eslint/no-extra-non-null-assertion	Disallow extra non-null assertion
@typescript-eslint/no-extra-parens	Disallow unnecessary parentheses		🔧
@typescript-eslint/no-extra-semi	Disallow unnecessary semicolons		🔧
@typescript-eslint/no-extraneous-class	Forbids the use of classes as namespaces
@typescript-eslint/no-floating-promises	Requires Promise-like values to be handled appropriately.			💭
@typescript-eslint/no-for-in-array	Disallow iterating over an array with a for-in loop	✔️		💭
@typescript-eslint/no-inferrable-types	Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean	✔️	🔧
@typescript-eslint/no-magic-numbers	Disallows magic numbers
@typescript-eslint/no-misused-new	Enforce valid definition of new and constructor	✔️
@typescript-eslint/no-misused-promises	Avoid using promises in places not designed to handle them	✔️		💭
@typescript-eslint/no-namespace	Disallow the use of custom TypeScript modules and namespaces	✔️
@typescript-eslint/no-non-null-assertion	Disallows non-null assertions using the ! postfix operator	✔️
@typescript-eslint/no-parameter-properties	Disallow the use of parameter properties in class constructors
@typescript-eslint/no-require-imports	Disallows invocation of require()
@typescript-eslint/no-this-alias	Disallow aliasing this	✔️
@typescript-eslint/no-type-alias	Disallow the use of type aliases
@typescript-eslint/no-unnecessary-condition	Prevents conditionals where the type is always truthy or always falsy		🔧	💭
@typescript-eslint/no-unnecessary-qualifier	Warns when a namespace qualifier is unnecessary		🔧	💭
@typescript-eslint/no-unnecessary-type-arguments	Warns if an explicitly specified type argument is the default for that type parameter		🔧	💭
@typescript-eslint/no-unnecessary-type-assertion	Warns if a type assertion does not change the type of an expression	✔️	🔧	💭
@typescript-eslint/no-untyped-public-signature	Requires that all public method arguments and return type will be explicitly typed
@typescript-eslint/no-unused-expressions	Disallow unused expressions
@typescript-eslint/no-unused-vars	Disallow unused variables	✔️
@typescript-eslint/no-unused-vars-experimental	Disallow unused variables and arguments.			💭
@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-var-requires	Disallows the use of require statements except in import statements	✔️
@typescript-eslint/prefer-for-of	Prefer a ‘for-of’ loop over a standard ‘for’ loop if the index is only used to access the array being iterated
@typescript-eslint/prefer-function-type	Use function types instead of interfaces with call signatures		🔧
@typescript-eslint/prefer-includes	Enforce includes method over indexOf method	✔️	🔧	💭
@typescript-eslint/prefer-namespace-keyword	Require the use of the namespace keyword instead of the module keyword to declare custom TypeScript modules	✔️	🔧
@typescript-eslint/prefer-nullish-coalescing	Enforce the usage of the nullish coalescing operator instead of logical chaining		🔧	💭
@typescript-eslint/prefer-optional-chain	Prefer using concise optional chain expressions instead of chained logical ands		🔧
@typescript-eslint/prefer-readonly	Requires that private members are marked as readonly if they're never modified outside of the constructor		🔧	💭
@typescript-eslint/prefer-regexp-exec	Prefer RegExp#exec() over String#match() if no global flag is provided	✔️		💭
@typescript-eslint/prefer-string-starts-ends-with	Enforce the use of String#startsWith and String#endsWith instead of other equivalent methods of checking substrings	✔️	🔧	💭
@typescript-eslint/promise-function-async	Requires any function or method that returns a Promise to be marked async			💭
@typescript-eslint/quotes	Enforce the consistent use of either backticks, double, or single quotes		🔧
@typescript-eslint/require-array-sort-compare	Enforce giving compare argument to Array#sort			💭
@typescript-eslint/require-await	Disallow async functions which have no await expression	✔️		💭
@typescript-eslint/restrict-plus-operands	When adding two variables, operands must both be of type number or of type string			💭
@typescript-eslint/restrict-template-expressions	Enforce template literal expressions to be of string type			💭
@typescript-eslint/return-await	Rules for awaiting returned promises			💭
@typescript-eslint/semi	Require or disallow semicolons instead of ASI		🔧
@typescript-eslint/space-before-function-paren	enforce consistent spacing before function definition opening parenthesis		🔧
@typescript-eslint/strict-boolean-expressions	Restricts the types allowed in boolean expressions			💭
@typescript-eslint/triple-slash-reference	Sets preference level for triple slash directives versus ES6-style import declarations	✔️
@typescript-eslint/type-annotation-spacing	Require consistent spacing around type annotations	✔️	🔧
@typescript-eslint/typedef	Requires type annotations to exist
@typescript-eslint/unbound-method	Enforces unbound methods are called with their expected scope	✔️		💭
@typescript-eslint/unified-signatures	Warns for any two overloads that could be unified into one by using a union or an optional/rest parameter

Contributing

See the contributing guide here