Framework to include localized messages into Google Apps Scripts

localized-message-framework-for-gas.md

How to Use

1. Prepare a copy of the code in the localized-message.js, setting MESSAGES to suit your needs.
2. To call a message,

// Get user locale
var locale = Session.getActiveUserLocale();

or alternatively, if you are creating a script bound to a Google Docs file (e.g., a Google Sheets file),

var locale = SpreadsheetApp.getActiveSpreadsheet().getSpreadsheetLocale();

Then create an object of the message in that locale

var localizedMessages = new LocalizedMessage(locale);

When calling a message,

console.log(localizedMessages.messageList.{{messageName}})

localized-message.js

// Set messages in their respective language as a global object.
const MESSAGES = {
  'en_US': {
    'messageName': 'messageContent in English'
  },
  'ja': {
    'messageName': '日本語のmessageContent'
  }
};

// Class to call the list of localized messages
class LocalizedMessage {
  constructor(userLocale = 'en_US') {
    this.locale = (MESSAGES[userLocale] ? userLocale : 'en_US');
    this.messageList = MESSAGES[this.locale];
    Object.keys(MESSAGES.en_US).forEach(key => {
      if (!this.messageList[key]) {
        this.messageList[key] = MESSAGES.en_US[key];
      }
    });
  }

  /**
   * Replace placeholder values in the designated text. String.prototype.replace() is executed using regular expressions with the 'global' flag on.
   * @param {string} text 
   * @param {array} placeholderValues Array of objects containing a placeholder string expressed in regular expression and its corresponding value.
   * @returns {string} The replaced text.
   */
  replacePlaceholders_(text, placeholderValues = []) {
    return placeholderValues.reduce((acc, cur) => acc.replace(new RegExp(cur.regexp, 'g'), cur.value), text);
  }

  /**
   * Replace placeholder string in this.messageList.hogefuga
   * @param {*} var1
   * @param {*} var2
   * @returns {string} The replaced text.
   */
  replaceHogefuga(var1, var2) {
    let text = this.messageList.hogefuga;
    let placeholderValues = [
      {
        'regexp': '\{\{var1\}\}',
        'value': var1
      },
      {
        'regexp': '\{\{var2\}\}',
        'value': var2
      }
    ];
    text = this.replacePlaceholders_(text, placeholderValues);
    return text;
  }
}