It's not pretty common. But, if you ever encounter such code, be sure it's a very bad practice. Introducing more scopes is a performance issue for JavaScript interpreter. It adds a new scope in the ladder. See the following sample scope:

function pageLoad()
{
    scope1();
    function scope1()
    {
        alert('scope1');
        scope2();
        
        function scope2()
        {
            alert('scope2');
        }
    }
}

Introducing more scopes enforces the interpreter to go through new more sections in the scope chain that it maintains for code execution. So, unnecessary scopes reduce performance and it's a bad design too.