Function-Scoped Functions aren't an ES6 feature

[Leon]

Placing a function declaration inside another function declaration has been valid JavaScript since Netscape 2.0, and moreover has never been disallowed by strict mode.

[Dr. Ralf S. Engelschall]

Yes, but not in strict mode since ES5. That's the point here. But I've made it more explicit now. Thanks for the feedback.

[Leon]

I just said:

it has never been disallowed by strict mode.

The only thing strict mode disallowed was block-scoped function declarations. Not function-scoped function declarations.

To summarise:
ALLOWED IN ES5:

"use strict"; function A() { function B() {} }

NOT ALLOWED IN ES5:

"use strict"; { function B() {} }

[Dr. Ralf S. Engelschall]

Ah, understood. You're right, I was wrong here. Now fixed. Thanks for clarification.