Include one file to another

Question

I'm looking for very simple template script for building JS files. It should do only one thing: include one file to another.

Template (main.js)

/*> script.js */

var style = "/*> style.css */";

script.js

var my_script;

style.css

html, body {margin:0; padding:0}
.my-style {background: #fffacc}

Output

var my_script;

var style = "html, body {margin:0; padding:0}\
.my-style {background: #fffacc}";

---

I've made cat main.js | sed -e 's!/\*> \(.*\) \*/!cat \1!g'. Output from it:

cat script.js

var style = "cat style.css";

How make cat \1 actually work?

I will use it for building UserJS (Greasemonkey scripts). I've few JS and CSS files in my repository. I would like to keep them separate from each other. But result script must be only one, so I need merge all JS and CSS files to it.

I can use sed, awk, perl or ruby.

---

Finally, I've made js-preprocessor. Thanks guys!

Answer 1

What’s the intended use for this? JavaScript does not support multi-line strings, so your style variable definition will result in a syntax error after that template expansion.

Edit: my mistake – I missed that your example expansion included a \ continuation. This complicates the expansion process though; it would be good if you could go into some more detail about where you plan to use this, what tools you have available etc.

An example in Ruby:

ruby <main.js -pe'$_.gsub!(%r{/\*>\s*(.+?)\s*\*/}) { File.read($1) }'

Answer 2

There are three obvious solutions:

1. Don't use any kind of include directive, merely specify the order of files. This lets you use a simple cat file1 file2 file3 > output statement to get the final result.
2. Use an existing preprocessor, such as the C preprocessor (cpp), but be careful of how it might interact with the JS. You can also use this to your advantage, however, by defining macros in "headers", as is already done for C, creating your own libraries.
3. Write a simple preprocessor that can do exactly what you want. If you just want to support #include-like directives, this would not be hard.

Non-obvious solutions might use some specific JavaScript engine which allowed you to add hooks or plugins to support file inclusion, outputting the resulting code, or maybe something else entirely.

Answer 3

I would use also ruby but I suggest to rely on erb which is included in ruby stdlib. It allows extensibility if you want to add more complex features.

In your case you could write the following method:

def include_file(filename)
  File.open( filename, "r" ) { |f| f.read }
end

And then use it from you template:

<% include_file "script.js"  %>
var style = "<% include_file "style.css"  %>";

It just works...