Why a Name Function Expression not available outside function body [duplicate]

Answer 1

Now, myNinja is a named function and as far as I know javascript allow the named function to go beyond the scope of its own function.

Only in a function declaration. It's specifically not the case for a named function expression. It's just how this is defined in the specification.

All the gory details are in the spec, the most relevant bit is:

NOTE The Identifier in a FunctionExpression can be referenced from inside the FunctionExpression's FunctionBody to allow the function to call itself recursively. However, unlike in a FunctionDeclaration, the Identifier in a FunctionExpression cannot be referenced from and does not affect the scope enclosing the FunctionExpression.

So if you changed your code to:

function myNinja() {
    console.log(typeof myNinja) //prints 'function'
}
var ninja = myNinja;
console.log(typeof myNinja) //prints 'function' (now we're using a declaration)

...since that uses a function declaration, myNinja is added to the scope in which it's defined. (The declaration is also hoisted, like all declarations; it's not processed as part of the step-by-step code the way expressions are.)