You Don’t Know JavaScript, Scope and Closures Chapter 5 Question, this code gives me an error

[yaranour333]

This code is from YDKJS book part 2 Scope and Clousers, when I run it it gives me an typeError that fn is not a function at bar(); why so?

function foo() {
  var a = 2;
  function baz() {
    console.log(a);
  }
  fn = baz;
}

function bar(fn) {
  fn();
}

foo();
bar();

[ILM]

@yaranour333

function bar(fn) {
  fn();
}

fn is the function parameter

@yaranour333

bar();

you are trying to call undefined, undefined is not a function

[yaranour333]

I have added
var fn;
at the beginning of the code and still get the same result

[ILM]

It’s a question of scope, fn is the name of the parameter of bar

@yaranour333

function bar(fn) {
  fn();
}

so when bar is called fn takes the value of whatever is passed as argument,

@yaranour333

bar();

no argument means that fn is undefined.

This fn has no relation with the fn in the global scope