Although Javascript does not force you to declare or initialize variables

[adakist]

Although Javascript does not force you to declare or initialize variables before you begin function statements, it is often very useful to do so. First, it allows you to document the purpose of each variable. This is not only good programming practice, it is also genuinely useful.

[brumbino]

When you return to a function six months after you wrote it you may not remember what the variable countme does, unless you explicitly document it as // array index variable. Second, if you explicitly declare each variable, then you have the opportunity to initialize them to some meaningful default value.