ESLint

[rogerxu]

ESLint - Pluggable JavaScript linter

[rogerxu]

Configuration

Configuring ESLint - ESLint - Pluggable JavaScript linter

If there are multiple configuration files in the same directory, ESLint will only use one. The priority order is:

1. .eslintrc.js
2. .eslintrc.yaml
3. .eslintrc.yml
4. .eslintrc.json - ESLint’s JSON files also allow JavaScript-style comments.
5. .eslintrc - Deprecated
6. package.json

.eslintrc.json

{
  "root": true,
  "parserOptions": {
    "ecmaVersion": 6,
    "sourceType": "script",
    "ecmaFeatures": {
      "impliedStrict": true
    }
  },
  "env": {
    "node": true,
    "es6": true
  },
  "globals": {},
  "extends": "eslint:recommended",
  "rules": {}
}

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Rules

List of available rules - ESLint - Pluggable JavaScript linter

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Possible Errors

• "for-direction": "error" - 4.0.0

• "getter-return": "error" - 4.2.0

• "no-async-promise-executor": "error" - 5.3.0

• "no-await-in-loop": "error" - 3.12.0

• "no-compare-neg-zero": "error" - 3.17.0

• "no-cond-assign": ["error", "except-parens"]

• "no-console": "error"

• "no-constant-condition": "error"

• "no-control-regex": "error"

• "no-debugger": "error"

• "no-dupe-args": "error"

• "no-dupe-keys": "error"

• "no-duplicate-case": "error"

• "no-empty": "error"

• "no-empty-character-class": "error"

• "no-ex-assign": "error"

• "no-extra-boolean-cast": "error"

• "no-extra-parens": "error"

• "no-extra-semi": "error"

• "no-func-assign": "error"

• "no-inner-declarations": "error"

• "no-invalid-regexp": "error"

• "no-irregular-whitespace": "error"

• "no-misleading-character-class": "error" - 5.3.0

• "no-obj-calls": "error"

• "no-prototype-builtins": "error"

• "no-regex-spaces": "error"

• "no-sparse-arrays": "error"

• "no-template-curly-in-string": "error" - 3.3.0

• "no-unexpected-multiline": "error"

• "no-unreachable": "error"

• "no-unsafe-finally": "error"

• "no-unsafe-negation": "error" - 3.3.0

• "require-atomic-updates": "error" - 5.3.0

• "use-isnan": "error"

• "valid-jsdoc": ["error", options]

  {
  "prefer": {
    "return": "returns"
  },
  "requireReturn": false,
  "requireReturnType": true,
  "requireParamDescription": true,
  "requireReturnDescription": true
  }

• "valid-typeof": "error"

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Best Practices

• "accessor-pairs": "error"

• "array-callback-return": "error"

• "block-scoped-var": "error"

• "class-methods-use-this": "error" - 3.4.0

• "complexity": ["error", 20]

• "consistent-return": "error"

• "curly": "error"

• "default-case": "error"

• "dot-location": ["error", "property"]

• "dot-notation": "error"

• "eqeqeq": ["error", "smart"]

• "guard-for-in": "error"

• "max-classes-per-file": "error" - 5.0.0

• "no-alert": "error"

• "no-caller": "error"

• "no-case-declarations": "error"

• "no-div-regex": "error"

• "no-else-return": "error"

• "no-empty-function": "error"

• "no-empty-pattern": "error"

• "no-eq-null": "error"

• "no-eval": "error"

• "no-extend-native": "error"

• "no-extra-bind": "error"

• "no-extra-label": "error"

• "no-fallthrough": "error"

• "no-floating-decimal": "error"

• "no-global-assign": "error" - 3.3.0

• "no-implicit-coercion": "error"

• "no-implicit-globals": "error"

• "no-implied-eval": "error"

• "no-invalid-this": "error"

• "no-iterator": "error"

• "no-labels": "error"

• "no-lone-blocks": "error"

• "no-loop-func": "error"

• "no-magic-numbers": ["warn", options]

  {
  "ignore": [-1, 0, 1],
  "detectObjects": true
  }

• "no-multi-spaces": "error"

• "no-multi-str": "error"

• "no-new": "error"

• "no-new-func": "error"

• "no-new-wrappers": "error"

• "no-octal": "error"

• "no-octal-escape": "error"

• "no-param-reassign": "error"

• "no-proto": "error"

• "no-redeclare": "error"

• "no-restricted-properties": "error" - 3.5.0

• "no-return-assign": ["error", "except-parens"]

• "no-return-await": "error" - 3.10.0

• "no-script-url": "error"

• "no-self-assign": "error"

• "no-self-compare": "error"

• "no-sequences": "error"

• "no-throw-literal": "error"

• "no-unmodified-loop-condition": "error"

• "no-unused-expressions": "error"

• "no-unused-labels": "error"

• "no-useless-call": "error"

• "no-useless-concat": "error"

• "no-useless-escape": "error"

• "no-useless-return": "error" - 3.9.0

• "no-void": "error"

• "no-warning-comments": "warn"

• "no-with": "error"

• "prefer-promise-reject-errors": "error" - 3.14.0

• "radix": "error"

• "require-await": "error" - 3.11.0

• "require-unicode-regexp": "error" - 5.3.0

• "vars-on-top": "off"

• "wrap-iife": ["error", "inside"]

• "yoda": "error"

Strict Mode

• "strict": ["error", "safe"]

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Variables

• "init-declarations": ["off", "always"]

• "no-delete-var": "error"

• "no-label-var": "error"

• "no-restricted-globals": "error"

• "no-shadow": "error"

• "no-shadow-restricted-names": "error"

• "no-undef": "error"

• "no-undef-init": "error"

• "no-undefined": "error"

• "no-unused-vars": ["error", options]

  {
  "vars": "all",
  "args": "after-used",
  "ignoreRestSiblings": false
  }

• "no-use-before-define": ["error", options]

  {
  "functions": false
  }

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Node.js and CommonJS

• "callback-return": "error"
• "global-require": "error"
• "handle-callback-err": "error"
• "no-buffer-constructor": "error" - 4.0.0
• "no-mixed-requires": "error"
• "no-new-require": "error"
• "no-path-concat": "error"
• "no-process-env": "error"
• "no-process-exit": "error"
• "no-restricted-modules": "error"
• "no-sync": "error"

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Stylistic Issues

• "array-bracket-newline": ["error", "consistent"] - 4.0.0

• "array-bracket-spacing": ["error", "never"]

• "array-element-newline" :["error", "consistent"] - 4.0.0

• "block-spacing": ["error", "always"]

• "brace-style": ["error", "1tbs", {"allowSingleLine": true}]

• "camelcase": ["error", {"properties": "always"}]

• "capitalized-comments": "off" - 3.11.0

• "comma-dangle": ["error", "always-multiline"]

• "comma-spacing": ["error", {"before": false, "after": true}]

• "comma-style": ["error", "last"]

• "computed-property-spacing": ["error", "never"]

• "consistent-this": ["error", "that"]

• "eol-last": ["error", "always"]

• "func-call-spacing": ["error", "never"] - 3.3.0

• "func-name-matching": ["error", "always"] - 3.8.0

• "func-names": ["error", "as-needed"]

• "func-style": ["error", "expression"]

• "function-paren-newline": ["error", "multiline"] - 4.6.0

• "id-blacklist": ["error", "e", "cb"]

• "id-length": "error"

• "id-match: "error"

• "implicit-arrow-linebreak": ["error", "beside"] - 4.12.0

• "indent": ["error", 2, {"SwitchCase": 1}]

• "jsx-quotes": ["error", "prefer-double"]

• "key-spacing": ["error", {"beforeColon": false, "afterColon": true, "mode": "strict"}]

• "keyword-spacing": ["error", {"before": true, "after": true}]

• "line-comment-position": ["off", {"position": "above"}] - 3.5.0

• "linebreak-style": ["error", "unix"],

• "lines-around-comment": ["error", options]

  {
  "beforeBlockComment": true,
  "beforeLineComment": true,
  "allowBlockStart": true,
  "allowObjectStart": true
  }

• "lines-between-class-members": ["error", "always"] - 4.9.0

• "max-depth": ["error", 4]

• "max-len": ["error", 200, 4]

• "max-lines: ["error", 1000]"

• "max-lines-per-function": ["warn", 50] - 5.0.0

• "max-nested-callbacks": ["error", 3]

• "max-params": ["error", 3]

• "max-statements": ["error", 20]

• "max-statements-per-line": ["error", {"max": 1}]

• "multiline-comment-style": ["error", "separate-lines"]

• "multiline-ternary": ["error", "always-multiline"]

• "new-cap": ["error", options]

  {
  "newIsCap": true,
  "capIsNew": true
  }

• "new-parens": "error"

• "newline-per-chained-call": ["error", {"ignoreChainWithDepth": 2}]

• "no-array-constructor": "error"

• "no-bitwise": "error"

• "no-continue": "error"

• "no-inline-comments": "off"

• "no-lonely-if": "error"

• "no-mixed-operators": "off"

• "no-mixed-spaces-and-tabs": "error"

• "no-multi-assign": "error" - 3.14.0

• "no-multiple-empty-lines": ["error", {"max": 2}]

• "no-negated-condition": "off"

• "no-nested-ternary": "error"

• "no-new-object": "error"

• "no-plusplus": "off"

• "no-restricted-syntax": "off"

• "no-tabs": "error"

• "no-ternary": "off"

• "no-trailing-spaces": "error"

• "no-underscore-dangle": "error"

• "no-unneeded-ternary": "error"

• "no-whitespace-before-property": "error"

• "nonblock-statement-body-position": "error" - 3.17.0

• "object-curly-newline": ["error", {"consistent": true}]

• "object-curly-spacing": ["error", "never"]

• "object-property-newline": "off"

• "one-var": "off"

• "one-var-declaration-per-line": ["error", "initializations"]

• "operator-assignment": ["error", "always"]

• "operator-linebreak": ["error", "before"]

• "padded-blocks": ["error", "never"]

• "padding-line-between-statements": ["error", options] - 4.0.0

  {
  "blankLine": "always",
  "prev": "*",
  "next": "return"
  }

• "prefer-object-spread": "error" - 5.0.0

• "quote-props": ["error", "as-needed"]

• "quotes": ["error", "single"]

• "require-jsdoc": ["warn", options]

  {
  "require": {
    "FunctionDeclaration": true,
    "MethodDefinition": false,
    "ClassDeclaration": false,
    "ArrowFunctionExpression": false
  }
  }

• "semi": ["error", "always"]

• "semi-spacing": ["error", options]

  {
  "before": false,
  "after": true
  }

• "semi-style": ["error", "last"] - 4.0.0

• "sort-keys": "off" - 3.3.0

• "sort-vars": "off"

• "space-before-blocks": ["error", "always"]

• "space-before-function-paren": ["error", options]

  {
  "anonymous": "always",
  "named": "never",
  "asyncArrow": "always"
  }

• "space-in-parens": ["error", "never"]

• "space-infix-ops": "error"

• "space-unary-ops": ["error", options]

  {
  "words": true,
  "nonwords": false
  }

• "spaced-comment": ["error", "always", options]

  {
  "exceptions": ["*"]
  }

• "switch-colon-spacing": ["error", options] - 4.0.0

  {
  "after": true,
  "before": false
  }

• "template-tag-spacing": ["error", "never"] - 3.15.0

• "unicode-bom": ["error", "never"]

• "wrap-regex": "off"

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ECMAScript 6

• "arrow-body-style": ["error", "as-needed"]

• "arrow-parens": ["error", "always"]

• "arrow-spacing": "error"

• "constructor-super": "error"

• "generator-star-spacing": ["error", options]

  {
  "before": true,
  "after": false
  }

• "no-class-assign": "error"

• "no-confusing-arrow": "error"

• "no-const-assign": "error"

• "no-dupe-class-members": "error"

• "no-duplicate-imports": "error"

• "no-new-symbol": "error"

• "no-restricted-imports": "error"

• "no-this-before-super": "error"

• "no-useless-computed-key": "error"

• "no-useless-constructor": "error"

• "no-useless-rename": "error"

• "no-var": "error"

• "object-shorthand": ["error", "always"]

• "prefer-arrow-callback": "error"

• "prefer-const": "error"

• "prefer-destructuring": "error" - 3.13.0

• "prefer-numeric-literals": "error"

• "prefer-rest-params": "error"

• "prefer-spread": "error"

• "prefer-template": "error"

• "require-yield": "error"

• "rest-spread-spacing": ["error", "never"]

• "sort-imports": "off"

• "symbol-description": "error"

• "template-curly-spacing": ["error", "never"]

• "yield-star-spacing": ["error", "after"]

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VS Code Extension

Microsoft/vscode-eslint: VSCode extension to integrate eslint into VSCode

Configuration

Node.js API - ESLint - Pluggable JavaScript linter

.vscode/settings.json

{
  "eslint.options": {
    "ignorePath": "app/.eslintignore",
    "rulePaths": ["app/node_modules/@sap/di.code-validation.js/src/defaultConfig/fioriCustomRules/.eslintrules"]
  },
}