prepin

> An in-place pre-processor for javascript files using C style pre-compile
syntax to compose custom builds from npm-packages.

[![NPM version][badge]][repo]

Pre-processors found on [npm][] require a different file for outputting
processed changes. This is not ideal for in-place custom builds on already
published packages. This pre-processors main purpose is to allow reduction of
package size for e.g. single-page apps on not requiring modules based on macros
given at transpile time.

Syntax

Follows C style pre-compiler syntax but requires // right in front to work in
.js files.

``
// #if expression // e.g. // #if macro == 1
// #if defined(macro)
// #ifdef macro
// #ifndef macro
// #elif expression // e.g. // #elif macro == 2
// #else
// #endif
// # is a commented line
`

Example

Let's assume a example/sample.js file, which includes a package of large size which is
required for a specific task is not used in a smaller custom build...

The original file:

`js
// #ifndef small
const big = require('./big-package')
// #else
// # let big // define the alternative
// #endif

if (big) {
// ...
}
`

If processing with prepin -m small sample.js you'll get:

`js
// #ifndef small
// # const big = require('./big-package')
// #else
let big // define the alternative
// #endif

if (big) {
// ...
}
`

CLI

`
prepin [options] [file]

Options:

-m macro=1 define macro
-o

write output to file

Examples:

cat sample.js | prepin -m small
reads from stdin and transpiles using macro "small", writes to stdout.

prepin -m small=1 -m other sample.js
pre-process with macros small=1, other on sample.js
`

API

`js
const Prepin = require('prepin')

const opts = {macros: {small: true}, input: 'sample.js', output: 'sample.js'}

new Prepin(opts).proc().catch((e) => console.error(e))
``

License

[UNLICENSE][]

[badge]: https://badge.fury.io/js/prepin.svg
[repo]: https://www.npmjs.com/package/prepin

[npm]: https://npmjs.org
[UNLICENSE]: http://unlicense.org