命名空间内的匿名函数

Question

I'm learning Typescript but I'm having a few issues trying to understand a few things.

I have seen this code:

module Games {

((): void => {

    alert("");
);
})();
}

but when complied to javascript I get the same result if I change it to the bellow:

module Games {

    alert("");
})();
}

Is there any reason why I would write something like in the first example, or is it just bad code.

Answer 1

In your example, there is no reason to do that.

In more general terms, setting up a function creates a local scope, which allows you to use variables with it in that are not accessible to the rest of the module. This reduces the risk of variables in different parts of the module overwriting each other because they share a name.

Answer 2

So starting with this working example...

module Games {
    ((): void => {
        alert("");
    })();
}

You currently end up with the following result when you compile your TypeScript to JavaScript - the module becomes and immediately invoked function expression...

var Games;
(function (Games) {
    (function () {
        alert("");
    })();
})(Games || (Games = {}));

Later on when you are targeting a later version of ECMAScript, you may find that the module is actually there in the JavaScript (as this is just early access to a feature that is planned for ECMAScript).

Unless you have a good reason to want that within the module, I would recommend the following adjustment...

module Games {

}

((): void => {
    alert("");
})();

I think this will survive future changes better.