Function expression ending with ; vs. not

When reading others code I have seen functions written both ending with a semi-colon and not ending with a semi-colon.

with:

var testFunction = function() {
  // magic happens here
};

without:

var testFunction = function() {
  // magic happens here
}

• ?: Is one more "technically" correct than the other?
• ?: Is there a speed advantage to one?
• ?: Do browsers not care and so it's just a style bleeding over from another language or an old format that used to be required for JavaScript functions?
• ?: #{question I hadn't considered开发者_运维百科 to ask here but you think I should have}

Update: I also found this very useful => https://developer.mozilla.org/en/JavaScript/Reference/Functions_and_function_scope

At it's root, what you have there is an assignment statement, and according to the Google Javascript Style Guide, all statements should end in a ;. Especially assignment statements. JSLint requires ; or else it won't pass.

There are two ways to define functions:

var testFunction = function() {
  // magic happens here
};

and

function testFunction(){
  // magic happens here
}

I believe it's better to end with a ; when you define it using a statement (first option), but not as a function definition (second option).

JS Parsers are pretty flexible, so YMMV.

I would consider it technically correct to have the ; semicolon terminate the function because you are executing a declarative statement. Though not required by the grammar, it is generally accepted that variable declarations be terminated with a ; semicolon. In this case, the "variable" just happens to be a function.

// As you do this
var i = 0;

// Also do this
var obj = function() {
  // aforementioned magic
};

It may also be worthy to note that, when declaring objects, each field is separated with a comma ,.

var obj = function() {
  magic1 : function() {},
  magic2 : function() {}, // <-- Similarly, comma is optional here...sorta
                          //     See Marcel's comment below.
};

Of course, for simple functions declarations, it could be considered "more technically correct" to not have it since it is not a linearly executed statement. (See excellent counterpoint in Google style guide, etc) In this case, the semicolon ; gets interpreted as an "empty" line of code, not an expression termination token.

With simple function declarations, leave it off:

function doMagic() {
  // aforementioned magic
}

Is one more "technically" correct than the other?

No. Technically you're assigning a value to a variable that happens to be a function, just the same as var x = 10. You can declare this with or without the ; and it's equally correct either way.

Is there a speed advantage to one?

I would be immensely surprised if there was a noticeable difference.

Do browsers not care and so it's just a style bleeding over from another language or an old format that used to be required for JavaScript functions?

Browsers don't care, it's just a quirk of the language.

question I hadn't considered to ask here but you think I should have

Which one is more readable, you say? I personally prefer to end statements with a ; because it feels right and is more clear about what you're doing. I come from Java-land, where this is required, but even when it isn't I think it's clearer to explicitly end the statement with a ;, so I include it.

But, as with any code style argument, it quickly becomes a matter of personal choice, and there be flamewars. Proceed with caution.