101 lines
2.0 KiB
Markdown
101 lines
2.0 KiB
Markdown
# prepin
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> An in-place pre-processor for javascript files using C style pre-compile
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syntax to compose custom builds from npm-packages.
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[![NPM version][badge]][repo]
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Pre-processors found on [npm][] require a different file for outputting
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processed changes. This is not ideal for in-place custom builds on already
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published packages. This pre-processors main purpose is to allow reduction of
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package size for e.g. single-page apps on not requiring modules based on macros
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given at transpile time.
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## Syntax
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Follows C style pre-compiler syntax but requires `//` right in front to work in
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.js files.
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```
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// #if expression // e.g. // #if macro == 1
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// #if defined(macro)
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// #ifdef macro
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// #ifndef macro
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// #elif expression // e.g. // #elif macro == 2
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// #else
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// #endif
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// # is a commented line
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```
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## Example
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Let's assume a `example/sample.js` file, which includes a package of large size which is
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required for a specific task is not used in a smaller custom build...
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The original file:
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```js
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// #ifndef small
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const big = require('./big-package')
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// #else
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// # let big // define the alternative
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// #endif
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if (big) {
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// ...
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}
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```
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If processing with `prepin -m small sample.js` you'll get:
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```js
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// #ifndef small
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// # const big = require('./big-package')
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// #else
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let big // define the alternative
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// #endif
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if (big) {
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// ...
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}
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```
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## CLI
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```
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prepin [options] [file]
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Options:
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-m macro=1 define macro
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-o <output> write output to file
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Examples:
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cat sample.js | prepin -m small
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reads from stdin and transpiles using macro "small", writes to stdout.
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prepin -m small=1 -m other sample.js
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pre-process with macros small=1, other on sample.js
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```
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## API
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```js
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const Prepin = require('prepin')
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const opts = {macros: {small: true}, input: 'sample.js', output: 'sample.js'}
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new Prepin(opts).proc().catch((e) => console.error(e))
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```
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## License
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[UNLICENSE][]
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[badge]: https://badge.fury.io/js/prepin.svg
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[repo]: https://www.npmjs.com/package/prepin
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[npm]: https://npmjs.org
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[UNLICENSE]: http://unlicense.org
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