CONTRIBUTING.md specifies the minimum supported Firefox version as 91.1.0.
Based on the caniuse.com data for ECMAScript features listed at https://gist.github.com/Julien-Marcou/156b19aea4704e1d2f48adafc6e2acbf, I determined the following minimum Firefox versions that support each ECMAScript version:
- ECMAScript 2018 (current setting) = Firefox 78
- ECMAScript 2019 = Firefox 64
- ECMAScript 2020 = Firefox 80
- ECMAScript 2021 = Firefox 79
- ECMAScript 2022 = Firefox 92
- ECMAScript 2023 = Firefox 104
- ECMAScript 2024 = Firefox 119+ (not exactly sure)
This project is using v7 of eslint which depends on v7 of espree for JavaScript parsing. espree v7 has a maximum ECMAScript support version of ECMAScript 2021.
Based on these findings, increasing the configured `parser.ecmaVersion` from `2018` to `2021` will allow using all JavaScript syntax supported in Firefox 91.1.0+ without raising eslint errors.
