.eslintrc.json

{
    "rules": {
        "curly": ["error"],
        "eol-last": ["error"],
        "keyword-spacing": ["error"],
        "linebreak-style": ["error", "unix"],
        "max-len": [
            "error",
            {
                "code": 100,
                "tabWidth": 4,
                "ignoreStrings": true,
                "ignoreRegExpLiterals": true,
                "ignoreUrls": true
            }
        ],
        "no-trailing-spaces": ["error", { "skipBlankLines": true }],
        "no-unused-vars": [
            "warn",
            {
                "args": "after-used",
                // Ignore vars starting with an underscore.
                "varsIgnorePattern": "^_",
                // Ignore arguments starting with an underscore.
                "argsIgnorePattern": "^_"
            }
        ],
        // Blockly uses for exporting symbols. no-self-assign added in eslint 5.
        "no-self-assign": ["off"],
        // Blockly uses single quotes except for JSON blobs, which must use double quotes.
        "quotes": ["off"],
        "semi": ["error", "always"],
        // Blockly doesn't have space before function paren when defining functions.
        "space-before-function-paren": ["error", "never"],
        // Blockly doesn't have space before function paren when calling functions.
        "func-call-spacing": ["error", "never"],
        "space-infix-ops": ["error"],
        // Blockly uses 'use strict' in files.
        "strict": ["off"],
        // Closure style allows redeclarations.
        "no-redeclare": ["off"],
        "valid-jsdoc": ["error", {"requireReturn": false}],
        "no-console": ["off"],
        "no-multi-spaces": ["error", { "ignoreEOLComments": true }],
        "operator-linebreak": ["error", "after"],
        "spaced-comment": ["error", "always", {
            "block": {
                "balanced": true
            },
            "exceptions": ["*"]
        }],
        // Blockly uses prefixes for optional arguments and test-only functions.
        "camelcase": ["error", {
            "properties": "never",
            "allow": ["^opt_", "^_opt_", "^testOnly_"]
        }],
        // Use clang-format for indentation by running `npm run format`.
        "indent": ["off"],
        // Blockly uses capital letters for some non-constructor namespaces.
        // Keep them for legacy reasons.
        "new-cap": ["off"],
        // Mostly use default rules for brace style, but allow single-line blocks.
        "brace-style": ["error", "1tbs", { "allowSingleLine": true }],
        // Blockly uses objects as maps, but uses Object.create(null) to
        // instantiate them.
        "guard-for-in": ["off"],
        "prefer-spread": ["off"],
        "comma-dangle": ["error", {
            "arrays": "always-multiline",
            "objects": "always-multiline",
            "imports": "always-multiline",
            "exports": "always-multiline",
            "functions": "ignore"
        }]
    },
    "env": {
        "es2020": true,
        "browser": true
    },
    "globals": {
        "Blockly": true,
        "goog": true,
        "exports": true
    },
    "extends": [
        "eslint:recommended", "google"
    ]
}