Javascript global function setting local variable

Question

Why does this return 'foo', not 'foobar'? I need function g to modify (non-global) var v, yet function g is a global function. Thanks.

f();

function f() {
  var v = 'foo';
  g(v);
  alert(v);
}

function g(v) {
  v = v+'bar';
  return v;
}

Answer 1

Because you return v from g(v) call but you do not reassign v

f();

function f() {
  var v = 'foo';
  v = g(v);  //you need to assign what is returned
  alert(v);
}

function g(v) {
  v = v+'bar';
  return v;
}

Answer 2

Because javascript only works by value, not by reference. See John Hartsock's answer.

Answer 3

Primitive ALL arguments in javascript (the string argument to g, in this case) are pass-by-value instead of pass-by-reference, which means the v you're working with in function g(v) is a copy of the v in function f.

Edit: all arguments are passed by value, not just primitives.