Javascript local and global variable confusion

In Javascript, the variable declarations are automatically moved to the top of the function. So, the interpreter would make it look more like this:

var myname = "initial"
function c(){
    var myname;
    // alerts undefined
    alert(myname);
    myname = "changed";
    // alerts changed
    alert(myname);
}
c();

This is called 'hoisting'.

Due to hoisting and the fact that the scope for any variable is the function it's declared in, it's standard practice to list all variables at the top of a function to avoid this confusion.