Rule proposal: Prefer `String#includes` over `String#indexOf`

With ES2015, it’s more succinct to use 'foobar'.includes('foo') instead of 'foobar'.indexOf('foo') !== -1 or 'foobar'.indexOf('foo') >= 0 for checking whether a string contains a substring. I would like a rule that enforces this in those two scenarios and the negative cases of that: 'foobar'.indexOf('foo') === -1 and 'foobar'.indexOf('foo') < 0.

Suggested rule name: prefer-string-includes

I think this would be a good rule as .includes makes the code intent clearer.

There’s already other rules that enforces new ES2015 features, so it seems natural to have a rule for this too.

[ilyavolodin]

This can now be implemented as an option for no-restricted-syntax rule:

"no-restricted-syntax": ["error", "BinaryExpression > CallExpression > MemberExpression > Identifier[name = 'indexOf']"]

So I don’t think this should be added to the core.

[nzakas]

Okay, it’s been another three months without movement, so closing.