Do we need a semicolon after function declaration? [duplicate]

Question

Possible Duplicate:
JavaScript: When should I use a semicolon after curly braces?

Someone added semicolon after function declaration, but someone not. Is this a good practice to add semicolon after function declaration?

function test(o) { }  function test(o) { }; 

Answer 1

A function declaration does not need (and should not have) a semicolon following it:

function test(o) { } 

However, if you write a function as an expression, like the variable initializer below, then the statement should be terminated with a semicolon, just like any other statement would be:

var a = function test(o) { }; 

See more about constructor vs declaration(statement) vs expression.

Answer 2

What's actually happening there is you're adding an empty statement after the function.

function test (o) { return o; }; 

could be seen as being similar to:

var test = 0;; 

That second semicolon isn't an error per-se. The browser treats it like a statement where absolutely nothing happened.

There are two things to keep in mind, here.

This applies ONLY to function-declarations and control-blocks (for/if/while/switch/etc).

Function-declarations should be defined at the bottom of your scope, so you don't run into problems like this:

function test () {} (function (window, document, undefined) { /* do stuff */ }(window, document)); 

Because the browser will assume that you mean function test() {}(/*return value of closure*/); Which is an error. A very bad and nasty error which is very easy to overlook.

But that's okay, because function-declarations can go under return statements and still work just fine.

So even if you wanted to go:

function doStuff () {     return (function () { /*process stuff*/ test(); }());     function test () {} } 

That's going to work just peachy.