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.)

Answer 2

Your function is being stored in the variable ninja, so you can't access it by the function name, only the variable name:

console.log(typeof ninja)

This differs from a function declaration like below, which in contrast can be accessed by the function name:

function ninja(){

}

There are other differences, such as the latter being 'hoisted', unlike the former.

Answer 3

No, the function is not a named function, it's a function expression.

A function expression can optionally have a name. Ref:

function [name]([param1[, param2[, ..., paramN]]]) {
   statements
}

Source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/function

About the function name:

name
The function name. Can be omitted, in which case the function is anonymous. The name is only local to the function body.

(Emphasis mine.)

A named function has a very similar syntax, but it's a declaration, not an expression.