What's the difference between these two approaches to namespacing?

问题

I've got the first file in my code directory as follows

myNamespace.js

var myNamespace = {};

Then my subsequent files can look as one of the two following ways.

first

(function (ns) {
    ns.DoStuff = function(){
        // do stuff
    }
})(myNamespace);

second

myNamespace.DoStuff = function(){
    //do stuff
}

So what is the difference between these two methods? Both seem to work for me. Is there a more generally accepted convention?

^{sorry, still new to javascript}

回答1:

You have an error in your first one, you've used this where I'm pretty sure you meant ns:

ns.DoStuff = function() {
};

Leaving that aside, your first approach tends to be better because you've created a nice little scoping function for yourself, which allows you to have private data and functions available to all of the public methods you create on your namespace, without making them globals. E.g.:

(function(ns) {
    function privateFunction() {
    }

    ns.DoStuff = function() {
        privateFunction();   // <=== works fine
    };

})(myNamespace);]
privateFunction(); // <=== doesn't work, because it's private

I like doing it that way partially because I have thing against anonymous functions, and so I wouldn't define DoStuff as above, but rather like this:

(function(ns) {
    ns.DoStuff = Namespace$DoStuff;
    function Namespace$DoStuff() {
    }
})(myNamespace);

Now the function I've assigned to myNamespace.DoStuff has a proper name, which helps me out when I'm debugging my code. But that name doesn't pollute the global namespace, which helps me stay sane and avoid conflicts with other code.

回答2:

Your first approach will not work. It would create DoStuff on the global object (most likely window). You would need to replace this with ns, after you did that, there is no difference between the two approaches.

The former will have the adventage that you might be able to closure all your application/file related stuff into that outer self-invoking closure function. So you won't clobber the global namespace.

(function (ns) {
    var foo = 10,
        bar = 42;

    ns.DoStuff = function(){
        console.log('foo is ', foo, ' and its not available globally');
    }
})(myNamespace);

来源：https://stackoverflow.com/questions/9264349/whats-the-difference-between-these-two-approaches-to-namespacing

标签

javascript

coding-style

namespaces