.eslintrc.js

const { resolve } = require('path')
module.exports = {
    // https://eslint.org/docs/user-guide/configuring#configuration-cascading-and-hierarchy
    // This option interrupts the configuration hierarchy at this file
    // Remove this if you have an higher level ESLint config file (it usually happens into a monorepos)
    root: true,

    // https://eslint.vuejs.org/user-guide/#how-to-use-custom-parser
    // Must use parserOptions instead of "parser" to allow vue-eslint-parser to keep working
    // `parser: 'vue-eslint-parser'` is already included with any 'plugin:vue/**' config and should be omitted
    parserOptions: {
        // https://github.com/typescript-eslint/typescript-eslint/tree/master/packages/parser#configuration
        // https://github.com/TypeStrong/fork-ts-checker-webpack-plugin#eslint
        // Needed to make the parser take into account 'vue' files
        extraFileExtensions: ['.svelte'],
        parser: '@typescript-eslint/parser',
        project: resolve(__dirname, './tsconfig.json'),
        tsconfigRootDir: __dirname,
        ecmaVersion: 2020, // Allows for the parsing of modern ECMAScript features
        sourceType: 'module', // Allows for the use of imports
    },
    env: {
        browser: true,
        es6: true,
        node: true,
    },

    // Rules order is important, please avoid shuffling them
    extends: [
        // Base ESLint recommended rules
        // 'eslint:recommended',

        // https://github.com/typescript-eslint/typescript-eslint/tree/master/packages/eslint-plugin#usage
        // ESLint typescript rules
        'plugin:@typescript-eslint/eslint-recommended',
        'plugin:@typescript-eslint/recommended',
        // consider disabling this class of rules if linting takes too long
        'plugin:@typescript-eslint/recommended-requiring-type-checking',

        'prettier',
    ],

    plugins: [
        // required to apply rules which need type information
        '@typescript-eslint',
    ],

    // add your custom rules here
    rules: {
        'prefer-promise-reject-errors': 'off',
        // allow paren-less arrow functions
        'arrow-parens': 'off',

        'no-nested-ternary': 'error',
        'no-unneeded-ternary': 'error',
        'brace-style': 'error',
        curly: 'error',
        eqeqeq: ['error', 'always', { 'null': 'ignore' }],

        // TypeScript
        quotes: ['warn', 'single', { avoidEscape: true }],
        '@typescript-eslint/explicit-function-return-type': 'off',
        '@typescript-eslint/explicit-module-boundary-types': 'off',

        // allow debugger during development only
        'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off',
    },
}