This text is superseded by https://gist.github.com/djedr/7d21eac05ce2bbbca29b29d532a1fbe4.
There are some reasons listed here. To expand on that, using the C preprocessor with JavaScript project also gives us an easy way to share constants between different files. Back-end (Node.js) and front-end (Angular, React). But you can also share constants between .js files and .css files or any other text formats. No fuss. Just #include "constants.cpp".
Macros that operate on plain text are more limited and sloppier than macros that operate on syntax trees, like sweet.js. But they are also simpler. And very often enough.
Also:
- cpp is simple
- anybody who wrote C, C++ or Objective-C used it and knows the basics
- it's widely available
- it's stable
Assuming you have the C preprocessor available from the command line under the cpp command, in order to invoke it in a JavaScript-friendly way, use it like so:
cpp input.cpp.js -P -nostdinc -o output.js
where:
-
input.cpp.jsis the name of the to-be-preprocessed input file, -
-Ptells the preprocessor (quoting the manpage):Inhibit generation of linemarkers in the output from the preprocessor. This might be useful when running the preprocessor on something that is not C code, and will be sent to a program which might be confused by the linemarkers.
-
-nostdinctells the preprocessor (quoting the man page):Do not search the standard system directories for header files. Only the directories you have specified with -I options (and the directory of the current file, if appropriate) are searched.
-
-o output.jsspecifies that the preprocessor's output will be written to a file namedoutput.js
See the above link again to see more options you might want to pass to the command and cpp's man page for explaination of these.
http://www.nongnu.org/espresso/js-cpp.html
https://rreverser.com/es6-modules-are-dead-long-live-c-preprocessor/
http://www.julienlecomte.net/blog/2007/09/16/