The book Learning JavaScript defines anonymous functions as follows...
Functions are objects. As such, you can create them - just like a
String
An anonymous function is simply a function with no name.
function(a, b){
return a + b;
}
The above code would be useless as it has no name to which you could call it with. So they are usually assigned to a variable.
var func = function(a, b){
return a + b;
}
This is helpful because you can pass an anonymous function to another function or method without having to create the function before hand, as demonstrated below.
function bob(a){
alert(a());
}
bob(function(){
return 10*10;
})