ESLint is a popular JavaScript linter that helps developers maintain a consistent coding style and catch potential errors. It works by analyzing your code and providing warnings or errors based on a set of defined rules. To use ESLint in your project
Run linting:
npm run lint
Run linting with fixing:
npm run lint --fix
ESLint Configuration Rules Explanation
Here is an explanation for each ESLint rule in the provided configuration:
Indentation:
Error if indentation is not 2 spaces.
Linebreak Style:
Error if linebreak style is not set to "unix."
Quotes:
Error for using anything other than single quotes, avoiding escape and disallowing template literals.
Semicolons:
Error if semicolons are missing.
Comma Dangle:
Error if there is no trailing comma in multiline object literals.
Comma Style:
Error if commas are not placed at the end of the last property.
No Multi-Spaces:
Error for multiple spaces, ignoring end-of-line comments.
No Unused Vars:
Error for unused variables, ignoring specified patterns.
Prefer Const:
Warning for using let or var instead of const when possible.
No Console:
Turn off the restriction for using console statements.
No Duplicate Imports:
Error if there are duplicate import statements.
Space Infix Ops:
Error for spaces around infix operators.
Arrow Spacing:
Error for spaces around arrow function arrows.
Comma Spacing:
Error for spacing around commas in parameter lists and array literals.
Space Before Function Paren:
Error for spacing before function parentheses.
Func Call Spacing:
Error for spacing in function calls.
Space In Parens:
Error for spaces inside parentheses.
Function Call Argument Newline:
Error for inconsistent newlines in function calls.
Space Before Blocks:
Error for spacing before blocks in functions and classes.
Keyword Spacing:
Error for spacing around keywords.
Brace Style:
Error for brace style not being "1tbs."
Object Curly Newline:
Error for inconsistent newlines in object literals.
Max Lines:
Error if a file exceeds 500 lines, skipping blank lines and comments.
Max Len:
Error if a line exceeds 120 characters, ignoring specific cases.
EOL Last:
Error if there's no newline at the end of the file.
ID Length:
Error if variable and function names are shorter than 2 or longer than 30 characters.
Max Lines Per Function:
Error if a function exceeds 50 lines.
No Var:
Warning for the use of the var keyword.
No Redefine:
Warning for redeclaring variables, including built-in globals.
No Shadow:
Warning for variable shadowing, including functions.
Block Scoped Var:
Warning for using var in block scope.
No Implicit Coercion:
Warning for implicit type coercion.
No Use Before Define:
Warning for using variables, functions, and classes before they are defined.
Array Callback Return:
Warning for missing return statements in array methods.
Init Declarations:
Warning for uninitialized variables (var without assignment).
No Loop Func:
Warning for functions declared inside loops using var.
No Trailing Spaces:
Error for trailing spaces at the end of lines.
Newline Before Return:
Error for a newline before the return statement.
Newline Per Chained Call:
Error for a newline per chained method call.
Object Property Newline:
Error for a newline after each property in object literals.
Operator Linebreak:
Error for placing line breaks before operators.
Spaced Comment:
Error for spaces after the // or /* in a comment.
Key Spacing:
Error for spacing between keys and values in object literals.
No Multiple Empty Lines:
Error for multiple empty lines, with a maximum of 2, and 1 at the end of the file.
Jest No Identical Title:
Error for identical Jest test titles.
Jest Valid Title:
Error for Jest test titles that are not valid.
React In JSX Scope:
Turn off the requirement to import React in JSX files.