# Guide

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ESLint rules which disallow each ECMAScript syntax.

# 🏁 Goal

Espree (opens new window), the default parser of ESLint (opens new window), has supported ecmaVersion option. However, the error messages of new syntax are not readable (e.g., "unexpected token" or something like).

When we use this plugin along with the latest ecmaVersion option value, it tells us the readable error message for the new syntax, such as "ES2020 BigInt is forbidden." Plus, this plugin lets us disable each syntactic feature individually.

# 💿 Installation

Use npm (opens new window) or a compatible tool.

npm install --save-dev eslint eslint-plugin-es

Requirements

  • Node.js 8.10.0 or newer.
  • ESLint 4.19.1 or newer.

# 📖 Usage

Configure your .eslintrc.* file.

For example, to enable only Rest/Spread Properties in ES2018, as similar to legacy experimentalObjectRestSpread option:

{
    "plugins": ["es"],
    "parserOptions": {
        "ecmaVersion": 2018
    },
    "rules": {
        "es/no-async-iteration": "error",
        "es/no-malformed-template-literals": "error",
        "es/no-regexp-lookbehind-assertions": "error",
        "es/no-regexp-named-capture-groups": "error",
        "es/no-regexp-s-flag": "error",
        "es/no-regexp-unicode-property-escapes": "error"
    }
}

# Presets

This plugin provides the following configs.

Config ID Description
plugin:es/restrict-to-es2019 disallow new stuff that ES2019 doesn't include.
plugin:es/restrict-to-es2018 disallow new stuff that ES2018 doesn't include.
plugin:es/restrict-to-es2017 disallow new stuff that ES2017 doesn't include.
plugin:es/restrict-to-es2016 disallow new stuff that ES2016 doesn't include.
plugin:es/restrict-to-es2015 disallow new stuff that ES2015 doesn't include.
plugin:es/restrict-to-es5 disallow new stuff that ES5 doesn't include.
plugin:es/restrict-to-es3 disallow new stuff that ES3 doesn't include.
plugin:es/no-new-in-es2020 disallow the new stuff in ES2020.
plugin:es/no-new-in-es2019 disallow the new stuff in ES2019.
plugin:es/no-new-in-es2018 disallow the new stuff in ES2018.
plugin:es/no-new-in-es2017 disallow the new stuff in ES2017.
plugin:es/no-new-in-es2016 disallow the new stuff in ES2016.
plugin:es/no-new-in-es2015 disallow the new stuff in ES2015.
plugin:es/no-new-in-es5 disallow the new stuff in ES5.
plugin:es/no-new-in-esnext disallow the new stuff to be planned for the next yearly ECMAScript snapshot.
⚠️ This config will be changed in the minor versions of this plugin.

For example:

{
    "parserOptions": {
        "ecmaVersion": 2021
    },
    "extends": [
        "eslint:recommended",
        "plugin:es/restrict-to-es2018"
    ],
    "rules": {
        "es/no-rest-spread-properties": "off"
    }
}