Why doesn't javascript have a better way to include files?

Question

I've seen a few ways that you can make a javascript file include other javascript files, but they all seem pretty hacky - mostly they involve tacking the javascript file onto the end of the current document and then loading it in some way.

Why doesn't javascript just include a simple "load this file and execute the script in it" include directive? It's not like this is a new concept. I know that everyone is excited about doing everything in HTML5 with javascript etc, but isn't it going to be hard if you have to hack around omission of basic functionality like this?

I can't see how it would be a security concern, since a web page can include as many javascript files as it likes, and they all get executed anyway.

Answer 1

The main problems with the current inclusion system (ie, add additional script tags) involve latency. Since a script tag can insert code at the point of inclusion, as soon as a script tag is encountered, further parsing has to more-or-less stop until the JS downloads and is executed (although the browser can continue to fetch resources in parallel). If the JS decides to run an inclusion, you've just added more latency on top of this - now you can't even fetch your scripts in parallel.

Basically, it's trying to solve a problem that doesn't exist (since JS can already tack on additional script tags to do an inclusion), while making the latency problem worse. There are javascript minifiers out there that can merge JS files; you should look into using those instead, as they will help improve latency issues as well.

Answer 2

Actually, YUI 3 solves this problem beautifully. Feel free to check out the documentation: http://developer.yahoo.com/yui/3/yui/#use (that's the specific Use function which does this magic). Basically it works like this:

• You define modules
• When you create the core YUI object with YUI(), you specify which modules your code needs
• Behind the scenes, YUI checks if those modules are loaded. If not, it asynchronously loads them on the page.

I've also read that the jQuery team's working on something similar (someone back me up here).

As to the philosophical argument that it'd be nice if this was built in, I think that may be a good feature. On the other hand, the simplicity of javascript is nice too. It allows a much lower point of entry for beginning programmers to do their thing. And for those of us that need it, great libraries like YUI are getting better every day.

Answer 3

the requirejs project attempts to solve this problem, please see for example

http://requirejs.org/docs/why.html

(I don't use it yet, though)