Conditional comments and variable replacement for rollup, based on jscc

rollup, rollup-plugin, javascript, typescript, es2019, es2015, es6, modules, compilation, preproccesor, jspreproc, jscc, preprocessor
npm install rollup-plugin-jscc@2.0.0



npm Version Build Status AppVeyor Status Maintainability Test coverage License

Conditional compilation and compile-time variable replacement for Rollup.

rollup-plugin-jscc is not a transpiler, it is a wrapper of jscc, a tiny and powerful, language agnostic file preprocessor that uses JavaScript to transform text based on expressions at compile time.

With jscc, you have:

  • Conditional inclusion/exclusion of blocks, based on compile-time variables*
  • Compile-time variables with all the power of JavaScript expressions
  • Replacement of variables in the sources, by its value at compile-time
  • Sourcemap support, useful for JavaScript sources.
  • TypeScript v3 definitions

* This feature allows you the conditional declaration of ES6 imports (See the example).

Since jscc is a preprocessor, rollup-plugin-jscc is implemented as a file loader, so it runs before any transpiler and is invisible to them. This behavior allows you to use it in a wide range of file types but, if necessary, it can be used as a Rollup transformer instead of a loader.


The removal of non-jscc comments is not included, but you can use rollup-plugin-cleanup, which brings compaction and normalization of lines in addition to the conditional removal of JS comments.

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npm i rollup-plugin-jscc -D
# or
yarn add rollup-plugin-jscc -D

rollup-plugin-jscc requires rollup v2.0 and node.js v10.12 or later.



import { rollup } from 'rollup'
import jscc from 'rollup-plugin-jscc'

export default {
  input: 'src/main.js',
  plugins: [
      values: { _APPNAME: 'My App', _DEBUG: 1 },
  //...other options

in your source:

/*#if _DEBUG
import mylib from 'mylib-debug';
//#else */
import mylib from 'mylib'

mylib.log('Starting $_APPNAME v$_VERSION...')


import mylib from 'mylib-debug'

mylib.log('Starting My App v1.0.0...')

That's it.

* jscc has two predefined memvars: _FILE and _VERSION, in addition to giving access to the environment variables through the nodejs proccess.env object.


Plain JavaScript object, with all properties optional.

Name Type Description
asloader boolean If false, run the plugin as a transformer, otherwise run as loader (the default).
escapeQuotes string String with the type of quotes to escape in the output of strings: 'single', 'double' or 'both'.
Default nothing.
keepLines boolean Preserves the empty lines of directives and blocks that were removed.
Use this option with sourceMap:false if you are interested only in keeping the line numbering.
Default false
mapHires boolean Make a hi-res source-map, if sourceMap:true (the default).
Default true
prefixes string | RegExp |
The start of a directive. That is the characters before the '#', usually the start of comments.
Default ['//', '/*', '<!--'] (with one optional space after them).
sourcemap boolean Must include a sourcemap?
Should be the same value as the property sourcemap of the Rollup output.
Default true
mapContent boolean Include the original source in the sourcemap, if sourceMap:true (the default).
Default true
values object Plain object defining the variables used by jscc during the preprocessing.
Default {}
extensions string | Array<string> Array of strings that specifies the file extensions to process.
Default ['js', 'jsx', 'ts', 'tsx', 'mjs', 'tag']
include string | Array<string> minimatch or array of minimatch patterns for paths that must be included in the processing.
exclude string | Array<string> minimatch or array of minimatch patterns for paths that should be ignored.


Please see the jscc wiki to know about directives used by jscc.

What's New

Please see the CHANGELOG.


The MIT License