mergeFiles.js

const fs = require('fs');

let language_code = 'en'; // en, de, el, es, fr, it, ja, ko, pt-PT, zh-CN

process.argv.forEach((val, index) => {
  if (index === 2) {
  	language_code_arr = ['en', 'de', 'el', 'es', 'fr', 'it', 'ja', 'ko', 'pt-PT', 'zh-CN'];
  	if (language_code_arr.includes(val)) {
  		language_code = val;
  	} else {
  		throw new Error('Unrecognised language!');
  	}
  }
});

const strings = require(`./translated_strings/${language_code}/strings`);
const strings2 = require(`./translated_strings/${language_code}/strings2`);
const strings3 = require(`./translated_strings/${language_code}/strings3`);
const new_strings = require(`./translated_strings/${language_code}/new strings`);
const website_strings = require(`./translated_strings/${language_code}/website_strings`);

fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,'{\n', (err)=>{
	if (err) throw err;
	// console.log('all_strings { is appended!');
});

for (var key in strings) {
  if (strings.hasOwnProperty(key)) {
  	var stringToPrint = '"' + key + '"' + ': ' + '"' + strings[key] + '"' + ',\n';
    fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,stringToPrint, (err)=>{
			if (err) throw err;
			// console.log('all_strings { is appended!');
		});
  }
}

// strings2
fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,'\n', (err)=>{
	if (err) throw err;
	// console.log('all_strings { is appended!');
});

for (var key in strings2) {
  if (strings2.hasOwnProperty(key)) {
  	var string2ToPrint = '"' + key + '"' + ': ' + '"' + strings2[key] + '"' + ',\n';
    fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,string2ToPrint, (err)=>{
			if (err) throw err;
			// console.log('all_strings { is appended!');
		});
  }
}

// strings3
fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,'\n', (err)=>{
	if (err) throw err;
	// console.log('all_strings { is appended!');
});

for (var key in strings3) {
  if (strings3.hasOwnProperty(key)) {
  	var string3ToPrint = '"' + key + '"' + ': ' + '"' + strings3[key] + '"' + ',\n';
    fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,string3ToPrint, (err)=>{
			if (err) throw err;
			// console.log('all_strings { is appended!');
		});
  }
}

// new_strings
fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,'\n', (err)=>{
	if (err) throw err;
	// console.log('all_strings { is appended!');
});

for (var key in new_strings) {
  if (new_strings.hasOwnProperty(key)) {
  	var newstringToPrint = '"' + key + '"' + ': ' + '"' + new_strings[key] + '"' + ',\n';
    fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,newstringToPrint, (err)=>{
			if (err) throw err;
			// console.log('all_strings { is appended!');
		});
  }
}

// website_strings
fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,'\n', (err)=>{
  if (err) throw err;
  // console.log('all_strings { is appended!');
});

for (var key in website_strings) {
  if (website_strings.hasOwnProperty(key)) {
    var websitestringToPrint = '"' + key + '"' + ': ' + '"' + website_strings[key] + '"' + ',\n';
    fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,websitestringToPrint, (err)=>{
      if (err) throw err;
      // console.log('all_strings { is appended!');
    });
  }
}

fs.appendFile(`./translated_strings/${language_code}/all_strings.json`,'}', (err)=>{
	if (err) throw err;
	// console.log('all_strings } is appended!');
});

console.log('all_strings.json is generated!');