Why do many javascript libraries begin with “(function () {”?

Question

Why do many javascript libraries look like this:

(function () { 
    /* code goes here */ 
})();

It appears to define an unnamed function whic

Answer 1

At a simple level it keeps the global namespace clean(er).

i.e.: It's effectively adding a layer of wrapping around the functions and variables within the library hence ensuring there aren't any namespace clashes with other functions that may be in use from other libraries, etc.