Custom ecmaVersion

[fanatid]

It is possible to set custom ecmaVersion in standard section in package.json? I want write package on ES5 and see error from standard if any feature from new ecma versions will be used.

[feross]

I am hesitant to add any additional configuration to standard, beyond what we already support. If you want to customize standard, I recommend extending the eslint shared config.

[dcposch]

I think this would be useful, too.

If you're running a project that needs to work everywhere without no transpiler, then you want the linter to tell you if you accidentally used an ES6 feature somewhere.

[dcposch]

For example, if you want to write a library that can run anywhere: in node, in the browser, in a web worker, then you could use

standard --env=builtin --ecmaVersion=5

...to make sure you're not using any Node globals (eg process), browser globals (eg window), or ES6 features (eg let).

[feross]

Re-opening for discussion.

[feross]

This is a cool idea but I think that we're rapidly approaching a world where we'll just start shipping ES6 and even ES7 directly to browsers, since support has gotten really good.

For example, take a look at how much support a feature like const has. 97%. Even super recent features like async functions already has 54% support, and that'll probably be 75% in a few months as Safari and Edge users continue upgrading to the latest version.

Also, we'll maybe eventually do a plugin system (without config!) (discussed in another issue) so that you can do npm install standard standard-es5 && standard and the linter will run with extra rules to force only ES5. This seems like a better approach than adding options to standard.