Sharable eslint config with strict rules (limited formatting)

Links

• npm package

Semver

• Patch version is incremented when existing rule is changed but eslint version is the same
• Minor version is incremented when config is updated to make use of new eslint rules or options. eslint dependency is also updated
• See eslint semver policy

Main features

• Rules are based on eslint version 8.21
• Most rules are configured in the strictest way possible with some exceptions
• Some rules are configured as warnings where a possible use case exists or when they are often broken during development
• Strict mode errors are checked for
• Most formatting rules are disabled
  • Some rules still conflict with prettier, notably no-mixed-operators
  • This config is meant to be used with dprint as formatter

Code smells

• Maximum cyclomatic complexity is 3
• Maximum nesting depth is 3
• Maximum number of lines in a file is 300 (excluding empty lines & comments)
• Maximum number of lines in a function is 50 (including empty lines & comments)
• Maximum number of params in a function is 4
• Maximum number of statements in a function is 20

Strictness

• Variable initialization is required
• Bitwise operators are forbidden
• eval is forbidden
• Short-hand type conversions are forbidden except for !! and +
• Magic numbers are forbidden (except for basic integers such as 1)
• Nested ternaries are allowed
• Shadowing variables is forbidden
• Explicit usage of undefined is forbidden (prefer null)
• var keyword is forbidden so its associated rules are disabled
• Constant assignment is preferred
• A number of regex strictness rules are applied

Style rules

• camelCase is enforced for variable names
• Some non-specific variable names (e.g. res) are discouraged
• Unused variables must be prefixed with _
• Variable & property name length should not exceed 30 characters
• comments are uncapitalized
• Each variable declaration requires a separate keyword
• Curly braces can be omitted after control statements if body is a single statement on the same line (if (foo) return)
• Function expressions are forbidden (prefer function declarations)
• Callbacks as arrow functions are preferred
• Object destructuring is preferred
• Imports are sorted
• Object keys are sorted if there are more than 10 of them (empty lines can be used to reset sorting)
• Blank lines are required between certain statement (e.g. before throw)