Constantine NPM

Constantine

Constantine is a package for copying constants from one language into a constants file for another language.

Getting Started

npm install -D constantine

import { copy } from 'constantine';

const srcFile = './server/src/main/java/constants/RestConstants.java';
const targetFile = './frontend/src/constants/restConstants.js';
copy(srcFile).to(targetFile);

Constantine will determine which parser and composer to use based on the file extension of the given paths.

Transforming Variable Names

Different languages have different variable naming conventions. You can use the transform function and some default provided cases to transform variables from one case into a different case.

Provided Cases:

camelCase
CAPS_CASE
PascalCase
snake_case

import {
    copy,
    camelCase,
    CAPS_CASE,
    transform
} from 'constantine';

const srcFile = './server/src/main/java/constants/RestConstants.java';
const targetFile = './frontend/src/constants/restConstants.js';
const transformer = transform(CAPS_CASE).to(camelCase);
copy(srcFile).with(transformer).to(targetFile);

You can even make your own custom transformer functions. Your custom transformer will receive an object where the keys are the variable names of the original file and values are those variable's values. Your function should also return and object with variable name to value mappings.

import { copy } from 'constantine';

const srcFile = './server/src/main/java/constants/RestConstants.java';
const targetFile = './frontend/src/constants/restConstants.js';

// Example custom transformer
//
// variableMap is an object with the variable names as keys and their
// corresponding values as values. This function also returns an object
// where the keys will be the end result variable names and the values
// will be the values for those variables.
const reverseTransformer = (variableMap) => {
    const variableNames = Object.keys(variableMap);
    return variableNames.reduce((acc, name) => {
        const key = name.split('').reverse().join('');
        acc[key] = variableMap[name];
        return acc;
    }, {})
}
copy(srcFile).with(reverseTransformer).to(targetFile);
/**
 * public static final String FOO_BAR = "/foo/bar";
 *
 * will turn into
 *
 * export const RAB_OOF = "/foo/bar";
 */

CLI

npm install -g constantine

constantine -f ./path/to/file.java -t ./path/to/file.js

Note: the cli does not support variable name transformers

With this java file as input

package foo;
public class RestConstants {
    // path params
    public static final String FIZZ_PARAM = "fizz";
    public static final String BAZ_PARAM="baz";

    // paths
    public static String FOO = "/foo";
    static final String FOO_BAR = "/foo/bar";
    static String FOO_101_BAR = "/foo/101/bar";
    // public static final String COMMENTED_CONSTANT = "/commented/constant";
    /**
    * export const COMMENTED_CONSTANT = "/commented/constant";
    */
    public static final String FOO_FIZZ = FOO + "/{" + FIZZ_PARAM + "}";
    public static final String POW = "/pow/"+BAZ_PARAM;
}

This javascript file will be outputted

export const FIZZ_PARAM = "fizz";
export const BAZ_PARAM = "baz";
export const FOO = "/foo";
export const FOO_BAR = "/foo/bar";
export const FOO_101_BAR = "/foo/101/bar";
export const FOO_FIZZ = FOO + "/{" + FIZZ_PARAM + "}";
export const POW = "/pow/"+BAZ_PARAM;