Functions can either be named or unnamed (anonymous functions):

var namedSum = function sum (a, b) { // named
    return a + b;
}

var anonSum = function (a, b) { // anonymous
    return a + b;
}

namedSum(1, 3);
anonSum(1, 3);

4 4

But their names are private to their own scope:

var sumTwoNumbers = function sum (a, b) {
    return a + b;
}

sum(1, 3);

Uncaught ReferenceError: sum is not defined

Named functions differ from the anonymous functions in multiple scenarios:

• When you are debugging, the name of the function will appear in the error/stack trace
• Named functions are hoisted while anonymous functions are not
• Named functions and anonymous functions behave differently when handling recursion
• Depending on ECMAScript version, named and anonymous functions may treat the function name property differently

Named functions are hoisted

When using an anonymous function, the function can only be called after the line of declaration, whereas a named function can be called before declaration. Consider

foo();
var foo = function () { // using an anonymous function
    console.log('bar');
}

Uncaught TypeError: foo is not a function

foo();
function foo () { // using a named function
    console.log('bar');
}

bar

Named Functions in a recursive scenario

A recursive function can be defined as: