Advantages to use function expression instead of function declaration?

Question

As seen here, there are some differences between function declaration and function expression.

A function expression has one disadvantage vs a function declaration, if called before its been declared it will give an error.

I would like to know only the advantages to use a function expression as I only seem to see the disadvantage I just named above. I possible with an example...

function expression:

alert(foo()); // ERROR! foo wasn't loaded yet
var foo = function() { return 5; } 

function declaration:

alert(foo()); // Alerts 5. Declarations are loaded before any code can run.
function foo() { return 5; } 

Answer 1

My Experiment: function expression we need to use when use that function in different scopes. For example.

function outer(){
       function inner(){

       }
}
outer();
inner();// Error ...calling inner..will not be found..

-this will not work. But

var inner;
function outer(){
 inner=function(){

       }
}
outer();
inner();// will work

-this will work

Answer 2

Along with that very good answer, the only advantage I can see is dynamically changing a function call.

For example this code :

function foo(){
    console.log('foo');
}

function bar(){
    console.log('bar');
}

var myFn = foo;

myFn();

setInterval(function(){
    if(myFn === foo) myFn = bar;
    else myFn = foo;
}, 5000);

setInterval(function(){
    myFn()
}, 6000);

It will never log the same thing since you reassign a global variable, every innerscope function will change while this code :

function foo(){
    console.log('foo');
}

setInterval(function(){
    function foo(){
        console.log('Changed foo');
    }

    foo()
}, 5000)

setInterval(function(){
    foo()
}, 5000)

Will log 2 different things. You can only change the current scope function, not the global.