Translate your App using ChatGPT OpenAI and i18n

npm install --save openai

npm install dotenv --save

require('dotenv').config()
const fs = require('fs')

const OpenAI = require('openai')

//make sure you have the OPENAI_API_KEY in your .env file
const OPENAI_API_KEY = process.env.OPENAI_API_KEY

const openai = new OpenAI({
  apiKey: OPENAI_API_KEY,
})

async function updateLanguageFile(english, fileName) {
  //get the .json file for the language using fileName
  let langJson = require(`./lang/${fileName}.json`)
  console.warn(`${fileName}.json:`)

  //get all empty keys for a language which need to be translated
  const emptyKeys = Object.keys(langJson).filter((key) => langJson[key] === '')

  if (emptyKeys.length > 0) {
    console.warn(`Translating using ChatGPT 3.5 Turbo...\n`)

    const englishEntries = {}

    //fetch the english sentences for all the missing empty keys
    //which would be sent to ChatGPT OpenAI api
    emptyKeys.forEach((ele) => {
      englishEntries[ele] = english[ele]
    })

    try {
      //Calls ChatGPT OpenAI api to translate the strings
      const translatedEntries = await completeTranslation(englishEntries, fileName)
      console.log(`en => ${JSON.stringify(englishEntries)}`)
      console.log(`${fileName} => ${translatedEntries}`)

      //append the freshly translated strings to the original language file
      langJson = { ...langJson, ...JSON.parse(translatedEntries) }
    } catch (translationError) {
      console.error(`Error translating:  ${translationError.message}`)
    }

    //sort the translations according to key name,
    //so that order is preserved in the language file
    const sortedLangJson = Object.keys(langJson)
      .sort()
      .reduce((acc, key) => {
        acc[key] = langJson[key]
        return acc
      }, {})

    //write it to the language file
    fs.writeFileSync(`./lang/${fileName}.json`, JSON.stringify(sortedLangJson, null, 2))
  } else {
    console.warn(`No translations missing`)
  }
  console.warn(`\n`)
}

const completeTranslation = async (messageObject, lang) => {
  try {
    /*This functions sends all the entries of a single language as a json object
    to ChatGPT OpenAI api and it returns you the translated object in json format.
    To save cost, I send the whole object in one request rather than
    sending each string individually which would cost more tokens.*/
    const completion = await openai.chat.completions.create({
      model: 'gpt-3.5-turbo', //You can use other models too
      messages: [
        //These are the prompts which I use for translations
        {
          role: 'system',
          content:
            'You will be provided with a json object in English language
             and your task is to only translate the values into the
             requested language, and return the result as valid json',
        },
        {
          role: 'user',
          content: `Translate the following json Object
          to '${lang}' language: ${JSON.stringify(messageObject)}`,
        },
      ],
      //better to not mess with these,
      //you can tweak token size if you want to send huge translation objects
      temperature: 1,
      max_tokens: 256,
      top_p: 1,
      frequency_penalty: 0,
      presence_penalty: 0,
    })

    return completion.choices[0].message.content
  } catch (error) {
    throw new Error(`Error completing translation: ${error.message}`)
  }
}

try {
  console.info(`Checking for missing translations\n`)
  const english = require('./lang/en.json') //path to your english .json file
  const languages = ['de', 'es', 'fr'] //names of you other language files.
  languages.forEach((lang) => {
    updateLanguageFile(english, lang)
  })
} catch (error) {
  console.error('Error reading JSON files:', error.message)
}