Preproc.js - The only preprocessor you will ever need.

What is preproc.js?

Preproc.js is an all in one preprocessor usable for all types of files. The expressions can be written in JavaScript and compiled from the command line or using node.js.
Try it out the example!

Usage

Command line

Install preproc.js:

foo@bar:~$ npm install -g preproc.js

Compile the source file:

foo@bar:~$ preproc <input-path>

Optionally specify an output path:

foo@bar:~$ preproc <input-path> -o <output-path>

Node.js

Install preproc.js:

foo@bar:~$ npm install preproc.js

Compile a string:

const parser = require('preproc');
const input = 'Current Date: {{ = new Date().toLocaleString() }}';
const result = parser.Parse(input, {});

console.log(result); // Current Date: 9.11.2020, 18:51:09

Preprocessor expressions

The preprocessor expressions can be written in JavaScript. All of them must be wrapped into double curly brackets {{ ... }}.

Executions

The : operator can be used to simply execute code:

{{ :
  const date = new Date();
  const timeString = date.toLocaleString();
}}
Current Date: {{ = timeString }}

Result: Current Date: 9.11.2020, 18:51:09

Assignments

The = operator can be used to return a given value:

Current Date: {{ = new Date().toLocaleString() }}

Result: Current Date: 9.11.2020, 18:51:09

Conditions

Use the keywords if, else if, else and end to output the inner text based on conditions:

{{ :
  const currentHour = new Date().getHours();
}}

{{ if currentHour <= 10 }}
Good morning!
{{ else if currentHour >= 18 }}
Good evening!
{{ else }}
Good day!
{{ end }}

Result: Good evening!

Command-line Options

Short	Full	Description
-V	--version	output the version number
-s	--set <variables...>	set one or more variables to be used. "-d foo=bar baz" can be retrieved using {{ = foo }}
-o	--output <path>	write the result into a file instead of the console
-h	--help	display help for command