fonteva-design-guide/force-app/main/default/lwc/multiLanguage/multiLanguage.js

## Dev, Build and Test

import Id from '@salesforce/user/Id';
import { updateRecord } from 'lightning/uiRecordApi';

const authenticatedUser = (userId, contactId, language) => {
    updateRecord({
        fields: {
            Id: userId,
            LanguageLocaleKey: language
        }
    })
        .then(user =>
            contactId
                ? updateRecord({
                      fields: {
                          Id: contactId,
                          OrderApi__Preferred_Language__c: language
                      }
                  })
                : null
        )
        .then(() => updateLangInURL(language))
        .catch(error => console.log(error));
};

const guestUser = (value) => updateLangInURL(value);

let updateLangInURL = (language) => {
    let languageCode = language.split('-')[0].replace(' ', '');
    let url = window.location.href;

    // replace old language UrlParam w/ new value
    const parts = window.location.search
        .split('&')
        .map(keyValue => (keyValue.includes('language=') ? `language=${languageCode.toLowerCase()}` : keyValue));

    // add language param if it doesn't exist
    if (!url.includes('language=')) {
        parts.push(`language=${languageCode.toLowerCase()}`);
    } else if (!parts[0].includes('?')) {
        // prepend question-mark if necessary
        parts[0] = '?' + parts[0];
    }

    window.location.search = parts.join('&');
};

export { authenticatedUser, guestUser };