Simplify regular expressions in i18n.t to make them non-polynomial

packages/govuk-frontend/src/govuk/i18n.mjs

@@ -33,7 +33,7 @@
    * @param {{ [key: string]: unknown }} [options] - Any options passed with the translation string, e.g: for string interpolation.
    * @returns {string} The appropriate translation string.
    * @throws {Error} Lookup key required
-   * @throws {Error} Options required for `${}` placeholders
+   * @throws {Error} Options required for `%{}` placeholders
    */
   t(lookupKey, options) {
     if (!lookupKey) {
@@ -58,9 +58,8 @@
     }
 
     if (typeof translation === 'string') {
-      // Check for ${} placeholders in the translation string
-      // eslint-disable-next-line @typescript-eslint/prefer-regexp-exec
-      if (translation.match(/%{(.\S+)}/)) {
+      // Check for %{} placeholders in the translation string
+      if (/%{(\S+)}/.test(translation)) {
         if (!options) {
           throw new Error(
             'i18n: cannot replace placeholders in string if no option data provided'
@@ -92,46 +91,46 @@
       ? new Intl.NumberFormat(this.locale)
       : undefined
 
     return translationString.replace(
-      /%{(.\S+)}/g,
+      /%{(\S+)}/g,
 
       /**
        * Replace translation string placeholders
        *
        * @internal
        * @param {string} placeholderWithBraces - Placeholder with braces
        * @param {string} placeholderKey - Placeholder key
        * @returns {string} Placeholder value
        */
       function (placeholderWithBraces, placeholderKey) {
         if (Object.prototype.hasOwnProperty.call(options, placeholderKey)) {
           const placeholderValue = options[placeholderKey]
 
           // If a user has passed `false` as the value for the placeholder
           // treat it as though the value should not be displayed
           if (
             placeholderValue === false ||
             (typeof placeholderValue !== 'number' &&
               typeof placeholderValue !== 'string')
           ) {
             return ''
           }
 
           // If the placeholder's value is a number, localise the number formatting
           if (typeof placeholderValue === 'number') {
             return formatter
               ? formatter.format(placeholderValue)
               : `${placeholderValue}`
           }
 
           return placeholderValue
         }
 
         throw new Error(
           `i18n: no data found to replace ${placeholderWithBraces} placeholder in string`
         )
       }
     )
   }
 
   /**