Extend i18n with translate and template literal

public/script.js

@@ -209,7 +209,7 @@ import {
     instruct_presets,
     selectContextPreset,
 } from './scripts/instruct-mode.js';
-import { initLocales } from './scripts/i18n.js';
+import { initLocales, t, translate } from './scripts/i18n.js';
 import { getFriendlyTokenizerName, getTokenCount, getTokenCountAsync, getTokenizerModel, initTokenizers, saveTokenCache } from './scripts/tokenizers.js';
 import {
     user_avatar,
@@ -7825,6 +7825,8 @@ window['SillyTavern'].getContext = function () {
         messageFormatting: messageFormatting,
         shouldSendOnEnter: shouldSendOnEnter,
         isMobile: isMobile,
+        t: t,
+        translate: translate,
         tags: tags,
         tagMap: tag_map,
         menuType: menu_type,

public/scripts/i18n.js

@@ -31,6 +31,49 @@ const observer = new MutationObserver(mutations => {
     });
 });
 
+/**
+ * Translates a template string with named arguments
+ *
+ * Uses the template literal with all values replaced by index placeholder for translation key.
+ *
+ * @example
+ * ```js
+ * toastr.warn(t`Tag ${tagName} not found.`);
+ * ```
+ * Should be translated in the translation files as:
+ * ```
+ * Tag ${0} not found. -> Tag ${0} nicht gefunden.
+ * ```
+ *
+ * @param {TemplateStringsArray} strings - Template strings array
+ * @param  {...any} values - Values for placeholders in the template string
+ * @returns {string} Translated and formatted string
+ */
+export function t(strings, ...values) {
+    let str = strings.reduce((result, string, i) => result + string + (values[i] !== undefined ? `\${${i}}` : ''), '');
+    let translatedStr = translate(str);
+
+    // Replace indexed placeholders with actual values
+    return translatedStr.replace(/\$\{(\d+)\}/g, (match, index) => values[index]);
+}
+
+/**
+ * Translates a given key or text
+ *
+ * If the translation is based on a key, that one is used to find a possible translation in the translation file.
+ * The original text still has to be provided, as that is the default value being returned if no translation is found.
+ *
+ * For in-code text translation on a format string, using the template literal `t` is preferred.
+ *
+ * @param {string} text - The text to translate
+ * @param {string?} key - The key to use for translation. If not provided, text is used as the key.
+ * @returns {string} - The translated text
+ */
+export function translate(text, key = null) {
+    const translationKey = key || text;
+    return localeData?.[translationKey] || text;
+}
+
 /**
  * Fetches the locale data for the given language.
  * @param {string} language Language code