Why are functions not available in global object?

Question

This script has different behavior based on whether it's run from the node js shell or stored in a script file passed to node.

Script:

var a = 1;
function b(){return 1;}
for(var k in global) console.log(k);

Output in shell (only last 4 lines are relevant IMO. Each of the 3 lines were copy/pasted sequentially into a node REPL instance running in Terminal on Mac OS X):

ArrayBuffer
Int8Array
Uint8Array
Int16Array
Uint16Array
Int32Array
Uint32Array
Float32Array
Float64Array
DataView
global
process
GLOBAL
root
Buffer
setTimeout
setInterval
clearTimeout
clearInterval
console
module
require
a
_
b
k

Output when run as a saved script (called node myscript.js from bash on Mac OS X):

ArrayBuffer
Int8Array
Uint8Array
Int16Array
Uint16Array
Int32Array
Uint32Array
Float32Array
Float64Array
DataView
global
process
GLOBAL
root
Buffer
setTimeout
setInterval
clearTimeout
clearInterval
console

Why are they different, and why can't my script see a and b in global?

EDIT: Adding an additional statement c = 2 changed the output. c was visible in both methods of running the script. This still doesn't explain a and b's presence when running the script from the shell though.

Answer 1

Basically it's because Node's REPL uses the "global" context as it's "this" (you can test that with global === this).

However, regular modules run in their own separate closure. So you can imagine it being something like this:

function (module, exports, global) {
  // your module code
}

So when you define a var in your and execute it as a script, you're really just defining it inside of a function closure. But in the REPL, you're defining the var at the global level.