Function declaration inside block scope overriding another function declaration

Question

Can someone explain why first function is running not the second one when I call it?

{
  function a() {
     console.log('first function')
  }
}

function a() {
     console.log('second function')
}

a()

If we declare them in a global scope they behave as expected, but inside block scope it's completely different. Why?

function a() {
     console.log('first function')
}

function a() {
     console.log('second function')
}

a()

FWIW, it gives "second function" in both cases for me… macOS Safari… — deceze, Jul 04 '22 at 08:10
This behavior is not consistent (node runs the second function for your first example, and throws an error for the second). — pilchard, Jul 04 '22 at 08:10
Functions aren't block scoped, so what exactly *is* the "expected behaviour"…? — deceze, Jul 04 '22 at 08:12
@deceze es6 introduced block scoped functions see: [What are the precise semantics of block-level functions in ES6?](https://stackoverflow.com/questions/31419897/what-are-the-precise-semantics-of-block-level-functions-in-es6) (also the reason the first example doesn't error in node as it doesn't see a conflict) — pilchard, Jul 04 '22 at 08:22
@pilchard *When* in strict mode, which doesn't doesn't appear to be… — deceze, Jul 04 '22 at 08:25

Nina Scholz · Answer 1 · 2022-07-04T08:15:18.770

1

The global function delaration move the function to top (hoisting), the one in the block stays at place.

The below result is from Edge 103.0.1264.37.

a(); // second

{
  function a() {
     console.log('first function')
  }
}

a(); // first

function a() {
     console.log('second function')
}

a(); // first

edited Jul 04 '22 at 08:15

answered Jul 04 '22 at 08:05

Nina Scholz

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This produces "second" three times in Safari… – deceze Jul 04 '22 at 08:10
@deceze, this is on Edge 103.0.1264.37. – Nina Scholz Jul 04 '22 at 08:13

Function declaration inside block scope overriding another function declaration

1 Answers1