_.all has an unecessary backward-incompatible change

[nickretallack]

I updated my underscore.js file today and my project broke. After a bit of debugging, I found out it's because _.all now requires the iterator argument, instead of it being optional. What is the point of this?

If no iterator is provided, why not use the identity iterator automatically? That would preserve backward compatibility. Also, it would allow me to use _.all all over the place without having to repeat that identity function argument every time for the simple case of checking my list items for truthiness.

[jashkenas]

... because we need to stick close to the ES5 API -- and the ES5 API requires the iterator argument, I'm afraid. You can take a look at the github issues to see the discusccion about the change.