Why do you need to invoke an anonymous function on the same line?

Question

I was reading some posts about closures and saw this everywhere, but there is no clear explanation how it works - everytime I was just told to use it...:

//          


        

Answer 1

The code you show,

(function (msg){alert(msg)});
('SO');

consist of two statements. The first is an expression which yields a function object (which will then be garbage collected because it is not saved). The second is an expression which yields a string. To apply the function to the string, you either need to pass the string as an argument to the function when it is created (which you also show above), or you will need to actually store the function in a variable, so that you can apply it at a later time, at your leisure. Like so:

var f = (function (msg){alert(msg)});
f('SO');

Note that by storing an anonymous function (a lambda function) in a variable, your are effectively giving it a name. Hence you may just as well define a regular function:

function f(msg) {alert(msg)};
f('SO');