This rule should prefer .includes() over .indexOf() when checking for existence. This would apply to the following types: String#includes, Array#includes, TypedArray#includes, Buffer#includes.

.includes() cases:

• 'foobar'.indexOf('foo') !== -1
• 'foobar'.indexOf('foo') != -1
• 'foobar'.indexOf('foo') > -1
• 'foobar'.indexOf('foo') >= 0

_{These would negate .includes():}

• 'foobar'.indexOf('foo') == -1
• 'foobar'.indexOf('foo') === -1
• 'foobar'.indexOf('foo') < 0

It would also be useful to catch cases where String#includes() would be better than a regex: /\r\n/.test(foo); => foo.includes('\r\n');

This was originally proposed for inclusion in ESLint, but declined for lack of type knowledge in JS.