Linter

Deno ships with a built in code linter for JavaScript and TypeScript.

  1. # lint all JS/TS files in the current directory and subdirectories
  2. deno lint
  3. # lint specific files
  4. deno lint myfile1.ts myfile2.ts
  5. # print result as JSON
  6. deno lint --json
  7. # read from stdin
  8. cat file.ts | deno lint -

For more detail, run deno lint --help.

Available rules

  • adjacent-overload-signatures
  • ban-ts-comment
  • ban-types
  • ban-untagged-ignore
  • camelcase
  • constructor-super
  • for-direction
  • getter-return
  • no-array-constructor
  • no-async-promise-executor
  • no-case-declarations
  • no-class-assign
  • no-compare-neg-zero
  • no-cond-assign
  • no-constant-condition
  • no-control-regex
  • no-debugger
  • no-delete-var
  • no-deprecated-deno-api
  • no-dupe-args
  • no-dupe-class-members
  • no-dupe-else-if
  • no-dupe-keys
  • no-duplicate-case
  • no-empty
  • no-empty-character-class
  • no-empty-interface
  • no-empty-pattern
  • no-ex-assign
  • no-explicit-any
  • no-extra-boolean-cast
  • no-extra-non-null-assertion
  • no-extra-semi
  • no-fallthrough
  • no-func-assign
  • no-global-assign
  • no-import-assign
  • no-inferrable-types
  • no-inner-declarations
  • no-invalid-regexp
  • no-irregular-whitespace
  • no-misused-new
  • no-mixed-spaces-and-tabs
  • no-namespace
  • no-new-symbol
  • no-obj-calls
  • no-octal
  • no-prototype-builtins
  • no-redeclare
  • no-regex-spaces
  • no-self-assign
  • no-setter-return
  • no-shadow-restricted-names
  • no-this-alias
  • no-this-before-super
  • no-unreachable
  • no-unsafe-finally
  • no-unsafe-negation
  • no-unused-labels
  • no-unused-vars
  • no-with
  • prefer-as-const
  • prefer-const
  • prefer-namespace-keyword
  • require-await
  • require-yield
  • use-isnan
  • valid-typeof

For more detail about each rule, visit the deno_lint rule documentation.

Ignore directives

Files

To ignore whole file // deno-lint-ignore-file directive should placed at the top of the file:

  1. // deno-lint-ignore-file
  3. function foo(): any {
  4.   // ...
  5. }

Ignore directive must be placed before first statement or declaration:

  1. // Copyright 2020 the Deno authors. All rights reserved. MIT license.
  3. /**
  4.  * Some JS doc
  5.  **/
  7. // deno-lint-ignore-file
  9. import { bar } from "./bar.js";
  11. function foo(): any {
  12.   // ...
  13. }

You can also ignore certain diagnostics in the whole file

  1. // deno-lint-ignore-file no-explicit-any no-empty
  3. function foo(): any {
  4.   // ...
  5. }

Diagnostics

To ignore certain diagnostic // deno-lint-ignore <codes...> directive should be placed before offending line. Specifying ignored rule name is required:

  1. // deno-lint-ignore no-explicit-any
  2. function foo(): any {
  3.   // ...
  4. }
  6. // deno-lint-ignore no-explicit-any explicit-function-return-type
  7. function bar(a: any) {
  8.   // ...
  9. }

Configuration

Starting with Deno v1.14 a linter can be customized using either a configuration file or following CLI flags:

  • --rules-tags - List of tag names that will be run. Empty list disables all tags and will only use rules from include. Defaults to “recommended”.

  • --rules-exclude - List of rule names that will be excluded from configured tag sets. If the same rule is in include it be run.

  • --rules-include - List of rule names that will be run. Even if the same rule is in exclude it will be run.