如何将多个文件放入单个命名空间/模块中？ （JavaScript的）

Question

I've been reading about the module pattern, but everything I read assumes that the entire contents of the module will be in a single file. I want to have one file per class.

I've resorted to doing this at the top of every file:

if(window.ModuleName === undefined) { window.ModuleName = {}; }

ModuleName.ClassName = function () { ... }

But this allows files to be included without their dependencies, which is also annoying. For example, lets say there is ClassA which uses ClassB , and "ClassB.js" is left out of the HTML, then ClassA will throw up errors. As far as I'm aware Javascript lacks an import statement, so in this case I actually want everything to be in a single file.

I assume that large javascript projects are broken up into multiple files, so there has to be a way around this. How is it generally done? Is there some tool that will combine multiple class files into a single module file?

Answer 1

This is a big topic but let me explain as much as I can. Javascript requires that you have preloaded anything you intended to use, which is why your module pattern has all the "things" in the same file. But if you plan to separate them in different files then you have to manage it before using. I suggest the following approaches

1. Concatenate them before serving them in the server. For example in jsp, you can create a servlet that returns contenttype = "text/javascript", inside that servlet you can append all the scripts you need in one dynamically generated script then return it to the client.

2. In your ant or maven builds etc, there are configurations where in you can concatenate them the files you want together. This is a common practice therefore you should find many reference in the internet.

3. Lazy-load javascripts. This is my preferred way. I use Lazyload javascript library . Basically I declare the dependencies of certain codes much like "import" in Java, then before i call any of them i load their dependencies. This allows for optimized dependency loading without scripts redundancies. The problem is you need to write some fairly complicated scripts to do this.

Hope to help.