Linter

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

Note: linter is a new feature and still unstable thus it requires --unstable flag

# lint all JS/TS files in the current directory and subdirectories
deno lint --unstable
# lint specific files
deno lint --unstable myfile1.ts myfile2.ts
# print result as JSON
deno lint --unstable --json
# read from stdin
cat file.ts | deno lint --unstable -

For more detail, run deno lint --help.

Available rules

• adjacent-overload-signatures
• ban-ts-comment
• ban-types
• ban-untagged-ignore
• 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-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-undef
• no-unreachable
• no-unsafe-finally
• no-unsafe-negation
• no-unused-labels
• no-with
• prefer-as-const
• prefer-namespace-keyword
• require-yield
• triple-slash-reference
• use-isnan
• valid-typeof

Ignore directives

Files

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

// deno-lint-ignore-file
function foo(): any {
  // ...
}

Ignore directive must be placed before first stament or declaration:

// Copyright 2020 the Deno authors. All rights reserved. MIT license.
/**
 * Some JS doc
 **/
// deno-lint-ignore-file
import { bar } from "./bar.js";
function foo(): any {
  // ...
}

You can also ignore certain diagnostics in the whole file

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

Diagnostics

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

// deno-lint-ignore no-explicit-any
function foo(): any {
  // ...
}
// deno-lint-ignore no-explicit-any explicit-function-return-type
function bar(a: any) {
  // ...
}

To provide some compatibility with ESLint deno lint also supports // eslint-disable-next-line directive. Just like with // deno-lint-ignore, it’s required to specify the ignored rule name:

// eslint-disable-next-line no-empty
while (true) {}
// eslint-disable-next-line @typescript-eslint/no-explicit-any
function bar(a: any) {
  // ...
}