.eslintrc

{
  // This file contains root configuration for ESLint. Its rules may be overriden in a specific
  // folder (e.g., tests) by placing .eslintrc in it.
  // All lint rules should be placed here unless they do not apply to entire JavaScript codebase.
  // For example, indentation rules should be here (applies to all JS files), but Protractor
  // should not (applies only to integration tests files).

  // Base rules on recommended ESLint settings.
  // TODO(bryk): Determine whether there is a better base config.
  "extends": "eslint:recommended",
  "env": {
    // Enables all ES6 features except modules.
    "es6": true,
  },
  "parserOptions": {
    // Enable ES6 modules to have all language features covered.
    "sourceType": "module"
  },
  "rules": {
    // Require parens in arrow function arguments.
    "arrow-parens": [2, "always"],
    // Require dangling comma at the end of any  multiline list/object. This is to be consistent
    // with backend code.
    "comma-dangle": [2, "always-multiline"],
    // Enforce newline consistency in member expressions. Dots are places on the same line as
    // the property.
    "dot-location": [2, "property"],
    // Enforce newline at the end of file, with no multiple empty lines.
    "eol-last": 2,
    // Force using === and !=== except when comparing to null. This is to prevent from bugs that
    // come from automatic type conversion in == operator and to be consistent across the codebase.
    "eqeqeq": [2, "allow-null"],
    // Require a capital letter for constructors.
    "new-cap": 2,
    // Disallow the omission of parentheses when invoking a constructor with no arguments.
    "new-parens": 2,
    // Disallow modifying constant variables.
    "no-const-assign": 2,
    // Disallow this keywords outside of classes or class-like objects.
    "no-invalid-this": 2,
    // Allow at most one newline between code blocks.
    "no-multiple-empty-lines": [2, {"max": 2, "maxEOF": 1}],
    // Disallow the use of ternary operators when a simpler alternative exists.
    "no-unneeded-ternary": 2,
    // Disallow trailing spaces. This is to unify code because editors may have different
    // settings.
    "no-trailing-spaces": 2,
    // Force using 'let' or 'const' instead of 'var'. This is to prevent from var hoisting bugs.
    "no-var": 2,
    // Require one variable declaration statement.
    "one-var": [2, "never"],
    // Prefer using template literals instead of strings concatenation.
    "prefer-template": 2,
    // Require use of the second argument for parseInt().
    "radix": 2,
    // Require semicolons in every place they are valid. This is to prevent from automatic
    // semicolon insertion bugs.
    "semi": [2, "always"],
    // Disallow setting strict mode in files. All JS code in the project uses ES6 modules so is
    // implicitly strict.
    "strict": [2, "never"],
    // Require valid JSDoc.
    "valid-jsdoc": [2, {
      "prefer": {
        "returns": "return"
      },
      "requireReturnDescription": false,
      "requireReturn": false,
      "requireParamDescription": false
    }],
    // No spacing in object literals nor in imports/exports.
    "object-curly-spacing": [2, "never"],
  },
}