prefer-arrow-callback: allowUnboundThis description may be confusing

http://eslint.org/docs/rules/prefer-arrow-callback#allowunboundthis

I’ve read this paragraph several times and by comparison with the code example it seems a bit confusing:

1. “When set to false, this option allows the use of this without restriction…”: does not the option apply more restrictions for using this?

2. “…checks for dynamically assigned this values…”: does “checks” mean “prohibits” or “allows”?

3. “Normally, the rule will flag…”: does “Normally” mean “true” or “false” for this option?

The code example is clear, but the description seems to be vague.

[not-an-aardvark]

Thanks for reporting, I agree that the documentation is unclear/misleading here. To answer your questions:

• The default behavior is {allowUnboundThis: true}. With the default behavior, the rule allows function expressions containing this, provided that they are not explicitly bound. This is because these functions would not be directly replaceable with arrow functions.

  foo(function() { this; }) // allowed by default
  foo(function() { this; }.bind(this)) // disallowed
  

• When allowUnboundThis is set to false, the rule imposes a stricter requirement by disallowing all function expressions containing this, even though those functions are not directly replaceable with arrow functions.

[webdevdaemon]

I just realized that i PR’d 4 commits rather than just one… I’m sure you’ll let me know if I need to fix that…

1000 apologies.

PR submitted though!