diff --git a/packages/govuk-frontend/src/govuk/components/accordion/accordion.mjs b/packages/govuk-frontend/src/govuk/components/accordion/accordion.mjs
index 8460784d11..839eaae053 100644
--- a/packages/govuk-frontend/src/govuk/components/accordion/accordion.mjs
+++ b/packages/govuk-frontend/src/govuk/components/accordion/accordion.mjs
@@ -15,107 +15,125 @@ import { I18n } from '../../i18n.mjs'
  * attribute, which also provides accessibility.
  */
 export class Accordion {
+  /** @private */
+  $module
+
   /**
-   * @param {Element} $module - HTML element to use for accordion
-   * @param {AccordionConfig} [config] - Accordion config
+   * @private
+   * @type {AccordionConfig}
    */
-  constructor ($module, config) {
-    if (!($module instanceof HTMLElement) || !document.body.classList.contains('govuk-frontend-supported')) {
-      return this
-    }
+  config
 
-    /** @private */
-    this.$module = $module
+  /** @private */
+  i18n
 
-    /**
-     * @private
-     * @type {AccordionConfig}
-     */
-    this.config = mergeConfigs(
-      Accordion.defaults,
-      config || {},
-      normaliseDataset($module.dataset)
-    )
+  /** @private */
+  controlsClass = 'govuk-accordion__controls'
 
-    /** @private */
-    this.i18n = new I18n(extractConfigByNamespace(this.config, 'i18n'))
+  /** @private */
+  showAllClass = 'govuk-accordion__show-all'
 
-    /** @private */
-    this.controlsClass = 'govuk-accordion__controls'
+  /** @private */
+  showAllTextClass = 'govuk-accordion__show-all-text'
 
-    /** @private */
-    this.showAllClass = 'govuk-accordion__show-all'
+  /** @private */
+  sectionClass = 'govuk-accordion__section'
 
-    /** @private */
-    this.showAllTextClass = 'govuk-accordion__show-all-text'
+  /** @private */
+  sectionExpandedClass = 'govuk-accordion__section--expanded'
 
-    /** @private */
-    this.sectionClass = 'govuk-accordion__section'
+  /** @private */
+  sectionButtonClass = 'govuk-accordion__section-button'
 
-    /** @private */
-    this.sectionExpandedClass = 'govuk-accordion__section--expanded'
+  /** @private */
+  sectionHeaderClass = 'govuk-accordion__section-header'
 
-    /** @private */
-    this.sectionButtonClass = 'govuk-accordion__section-button'
+  /** @private */
+  sectionHeadingClass = 'govuk-accordion__section-heading'
 
-    /** @private */
-    this.sectionHeaderClass = 'govuk-accordion__section-header'
+  /** @private */
+  sectionHeadingDividerClass = 'govuk-accordion__section-heading-divider'
 
-    /** @private */
-    this.sectionHeadingClass = 'govuk-accordion__section-heading'
+  /** @private */
+  sectionHeadingTextClass = 'govuk-accordion__section-heading-text'
 
-    /** @private */
-    this.sectionHeadingDividerClass = 'govuk-accordion__section-heading-divider'
+  /** @private */
+  sectionHeadingTextFocusClass = 'govuk-accordion__section-heading-text-focus'
 
-    /** @private */
-    this.sectionHeadingTextClass = 'govuk-accordion__section-heading-text'
+  /** @private */
+  sectionShowHideToggleClass = 'govuk-accordion__section-toggle'
 
-    /** @private */
-    this.sectionHeadingTextFocusClass = 'govuk-accordion__section-heading-text-focus'
+  /** @private */
+  sectionShowHideToggleFocusClass = 'govuk-accordion__section-toggle-focus'
 
-    /** @private */
-    this.sectionShowHideToggleClass = 'govuk-accordion__section-toggle'
+  /** @private */
+  sectionShowHideTextClass = 'govuk-accordion__section-toggle-text'
 
-    /** @private */
-    this.sectionShowHideToggleFocusClass = 'govuk-accordion__section-toggle-focus'
+  /** @private */
+  upChevronIconClass = 'govuk-accordion-nav__chevron'
 
-    /** @private */
-    this.sectionShowHideTextClass = 'govuk-accordion__section-toggle-text'
+  /** @private */
+  downChevronIconClass = 'govuk-accordion-nav__chevron--down'
 
-    /** @private */
-    this.upChevronIconClass = 'govuk-accordion-nav__chevron'
+  /** @private */
+  sectionSummaryClass = 'govuk-accordion__section-summary'
 
-    /** @private */
-    this.downChevronIconClass = 'govuk-accordion-nav__chevron--down'
+  /** @private */
+  sectionSummaryFocusClass = 'govuk-accordion__section-summary-focus'
 
-    /** @private */
-    this.sectionSummaryClass = 'govuk-accordion__section-summary'
+  /** @private */
+  sectionContentClass = 'govuk-accordion__section-content'
 
-    /** @private */
-    this.sectionSummaryFocusClass = 'govuk-accordion__section-summary-focus'
+  /** @private */
+  $sections
 
-    /** @private */
-    this.sectionContentClass = 'govuk-accordion__section-content'
+  /** @private */
+  browserSupportsSessionStorage = false
 
-    const $sections = this.$module.querySelectorAll(`.${this.sectionClass}`)
-    if (!$sections.length) {
+  /**
+   * @private
+   * @type {HTMLButtonElement | null}
+   */
+  $showAllButton = null
+
+  /**
+   * @private
+   * @type {HTMLSpanElement | null}
+   */
+  $showAllIcon = null
+
+  /**
+   * @private
+   * @type {HTMLSpanElement | null}
+   */
+  $showAllText = null
+
+  /**
+   * @param {Element} $module - HTML element to use for accordion
+   * @param {AccordionConfig} [config] - Accordion config
+   */
+  constructor ($module, config) {
+    if (!($module instanceof HTMLElement) || !document.body.classList.contains('govuk-frontend-supported')) {
       return this
     }
 
-    /** @private */
-    this.$sections = $sections
+    this.$module = $module
 
-    /** @private */
-    this.browserSupportsSessionStorage = helper.checkForSessionStorage()
+    this.config = mergeConfigs(
+      Accordion.defaults,
+      config || {},
+      normaliseDataset($module.dataset)
+    )
 
-    /** @private */
-    this.$showAllButton = null
+    this.i18n = new I18n(extractConfigByNamespace(this.config, 'i18n'))
 
-    /** @private */
-    this.$showAllIcon = null
+    const $sections = this.$module.querySelectorAll(`.${this.sectionClass}`)
+    if (!$sections.length) {
+      return this
+    }
 
-    /** @private */
-    this.$showAllText = null
+    this.$sections = $sections
+    this.browserSupportsSessionStorage = helper.checkForSessionStorage()
   }
 
   /**
diff --git a/packages/govuk-frontend/src/govuk/components/button/button.mjs b/packages/govuk-frontend/src/govuk/components/button/button.mjs
index daba236832..99af1fbef9 100644
--- a/packages/govuk-frontend/src/govuk/components/button/button.mjs
+++ b/packages/govuk-frontend/src/govuk/components/button/button.mjs
@@ -8,6 +8,21 @@ const DEBOUNCE_TIMEOUT_IN_SECONDS = 1
  * JavaScript enhancements for the Button component
  */
 export class Button {
+  /** @private */
+  $module
+
+  /**
+   * @private
+   * @type {ButtonConfig}
+   */
+  config
+
+  /**
+   * @private
+   * @type {number | null}
+   */
+  debounceFormSubmitTimer = null
+
   /**
    *
    * @param {Element} $module - HTML element to use for button
@@ -18,16 +33,8 @@ export class Button {
       return this
     }
 
-    /** @private */
     this.$module = $module
 
-    /** @private */
-    this.debounceFormSubmitTimer = null
-
-    /**
-     * @private
-     * @type {ButtonConfig}
-     */
     this.config = mergeConfigs(
       Button.defaults,
       config || {},
diff --git a/packages/govuk-frontend/src/govuk/components/character-count/character-count.mjs b/packages/govuk-frontend/src/govuk/components/character-count/character-count.mjs
index a8b01bdf03..203a201c06 100644
--- a/packages/govuk-frontend/src/govuk/components/character-count/character-count.mjs
+++ b/packages/govuk-frontend/src/govuk/components/character-count/character-count.mjs
@@ -14,6 +14,51 @@ import { I18n } from '../../i18n.mjs'
  * of the available characters/words has been entered.
  */
 export class CharacterCount {
+  /** @private */
+  $module
+
+  /** @private */
+  $textarea
+
+  /**
+   * @private
+   * @type {HTMLDivElement | null}
+   */
+  $visibleCountMessage = null
+
+  /**
+   * @private
+   * @type {HTMLDivElement | null}
+   */
+  $screenReaderCountMessage = null
+
+  /**
+   * @private
+   * @type {number | null}
+   */
+  lastInputTimestamp = null
+
+  /** @private */
+  lastInputValue = ''
+
+  /**
+   * @private
+   * @type {number | null}
+   */
+  valueChecker = null
+
+  /**
+   * @private
+   * @type {CharacterCountConfig}
+   */
+  config
+
+  /** @private */
+  i18n
+
+  /** @private */
+  maxLength = Infinity
+
   /**
    * @param {Element} $module - HTML element to use for character count
    * @param {CharacterCountConfig} [config] - Character count config
@@ -51,10 +96,6 @@ export class CharacterCount {
       }
     }
 
-    /**
-     * @private
-     * @type {CharacterCountConfig}
-     */
     this.config = mergeConfigs(
       CharacterCount.defaults,
       config || {},
@@ -62,14 +103,11 @@ export class CharacterCount {
       datasetConfig
     )
 
-    /** @private */
     this.i18n = new I18n(extractConfigByNamespace(this.config, 'i18n'), {
       // Read the fallback if necessary rather than have it set in the defaults
       locale: closestAttributeValue($module, 'lang')
     })
 
-    /** @private */
-    this.maxLength = Infinity
     // Determine the limit attribute (characters or words)
     if ('maxwords' in this.config && this.config.maxwords) {
       this.maxLength = this.config.maxwords
@@ -79,26 +117,8 @@ export class CharacterCount {
       return this
     }
 
-    /** @private */
     this.$module = $module
-
-    /** @private */
     this.$textarea = $textarea
-
-    /** @private */
-    this.$visibleCountMessage = null
-
-    /** @private */
-    this.$screenReaderCountMessage = null
-
-    /** @private */
-    this.lastInputTimestamp = null
-
-    /** @private */
-    this.lastInputValue = ''
-
-    /** @private */
-    this.valueChecker = null
   }
 
   /**
diff --git a/packages/govuk-frontend/src/govuk/components/checkboxes/checkboxes.mjs b/packages/govuk-frontend/src/govuk/components/checkboxes/checkboxes.mjs
index 8b4a6b1767..48298a6985 100644
--- a/packages/govuk-frontend/src/govuk/components/checkboxes/checkboxes.mjs
+++ b/packages/govuk-frontend/src/govuk/components/checkboxes/checkboxes.mjs
@@ -2,6 +2,12 @@
  * Checkboxes component
  */
 export class Checkboxes {
+  /** @private */
+  $module
+
+  /** @private */
+  $inputs
+
   /**
    * @param {Element} $module - HTML element to use for checkboxes
    */
@@ -16,10 +22,7 @@ export class Checkboxes {
       return this
     }
 
-    /** @private */
     this.$module = $module
-
-    /** @private */
     this.$inputs = $inputs
   }
 
diff --git a/packages/govuk-frontend/src/govuk/components/error-summary/error-summary.mjs b/packages/govuk-frontend/src/govuk/components/error-summary/error-summary.mjs
index 6359ad20d6..56459579d3 100644
--- a/packages/govuk-frontend/src/govuk/components/error-summary/error-summary.mjs
+++ b/packages/govuk-frontend/src/govuk/components/error-summary/error-summary.mjs
@@ -7,6 +7,15 @@ import { normaliseDataset } from '../../common/normalise-dataset.mjs'
  * Takes focus on initialisation for accessible announcement, unless disabled in configuration.
  */
 export class ErrorSummary {
+  /** @private */
+  $module
+
+  /**
+   * @private
+   * @type {ErrorSummaryConfig}
+   */
+  config
+
   /**
    *
    * @param {Element} $module - HTML element to use for error summary
@@ -24,13 +33,8 @@ export class ErrorSummary {
       return this
     }
 
-    /** @private */
     this.$module = $module
 
-    /**
-     * @private
-     * @type {ErrorSummaryConfig}
-     */
     this.config = mergeConfigs(
       ErrorSummary.defaults,
       config || {},
diff --git a/packages/govuk-frontend/src/govuk/components/header/header.mjs b/packages/govuk-frontend/src/govuk/components/header/header.mjs
index a25e598f67..803b028c74 100644
--- a/packages/govuk-frontend/src/govuk/components/header/header.mjs
+++ b/packages/govuk-frontend/src/govuk/components/header/header.mjs
@@ -2,6 +2,35 @@
  * Header component
  */
 export class Header {
+  /** @private */
+  $module
+
+  /** @private */
+  $menuButton
+
+  /** @private */
+  $menu
+
+  /**
+   * Save the opened/closed state for the nav in memory so that we can
+   * accurately maintain state when the screen is changed from small to
+   * big and back to small
+   *
+   * @private
+   */
+  menuIsOpen = false
+
+  /**
+   * A global const for storing a matchMedia instance which we'll use to
+   * detect when a screen size change happens. We set this later during the
+   * init function and rely on it being null if the feature isn't available
+   * to initially apply hidden attributes
+   *
+   * @private
+   * @type {MediaQueryList | null}
+   */
+  mql = null
+
   /**
    * @param {Element} $module - HTML element to use for header
    */
@@ -10,35 +39,11 @@ export class Header {
       return this
     }
 
-    /** @private */
     this.$module = $module
-
-    /** @private */
     this.$menuButton = $module.querySelector('.govuk-js-header-toggle')
-
-    /** @private */
     this.$menu = this.$menuButton && $module.querySelector(
       `#${this.$menuButton.getAttribute('aria-controls')}`
     )
-
-    /**
-     * Save the opened/closed state for the nav in memory so that we can
-     * accurately maintain state when the screen is changed from small to
-     * big and back to small
-     *
-     * @private
-     */
-    this.menuIsOpen = false
-
-    /**
-     * A global const for storing a matchMedia instance which we'll use to
-     * detect when a screen size change happens. We set this later during the
-     * init function and rely on it being null if the feature isn't available
-     * to initially apply hidden attributes
-     *
-     * @private
-     */
-    this.mql = null
   }
 
   /**
diff --git a/packages/govuk-frontend/src/govuk/components/notification-banner/notification-banner.mjs b/packages/govuk-frontend/src/govuk/components/notification-banner/notification-banner.mjs
index 81a946ea87..7fdee3ac74 100644
--- a/packages/govuk-frontend/src/govuk/components/notification-banner/notification-banner.mjs
+++ b/packages/govuk-frontend/src/govuk/components/notification-banner/notification-banner.mjs
@@ -5,6 +5,15 @@ import { normaliseDataset } from '../../common/normalise-dataset.mjs'
  * Notification Banner component
  */
 export class NotificationBanner {
+  /** @private */
+  $module
+
+  /**
+   * @private
+   * @type {NotificationBannerConfig}
+   */
+  config
+
   /**
    * @param {Element} $module - HTML element to use for notification banner
    * @param {NotificationBannerConfig} [config] - Notification banner config
@@ -14,13 +23,8 @@ export class NotificationBanner {
       return this
     }
 
-    /** @private */
     this.$module = $module
 
-    /**
-     * @private
-     * @type {NotificationBannerConfig}
-     */
     this.config = mergeConfigs(
       NotificationBanner.defaults,
       config || {},
diff --git a/packages/govuk-frontend/src/govuk/components/radios/radios.mjs b/packages/govuk-frontend/src/govuk/components/radios/radios.mjs
index e95ad436ba..52576d0364 100644
--- a/packages/govuk-frontend/src/govuk/components/radios/radios.mjs
+++ b/packages/govuk-frontend/src/govuk/components/radios/radios.mjs
@@ -2,6 +2,12 @@
  * Radios component
  */
 export class Radios {
+  /** @private */
+  $module
+
+  /** @private */
+  $inputs
+
   /**
    * @param {Element} $module - HTML element to use for radios
    */
@@ -16,10 +22,7 @@ export class Radios {
       return this
     }
 
-    /** @private */
     this.$module = $module
-
-    /** @private */
     this.$inputs = $inputs
   }
 
diff --git a/packages/govuk-frontend/src/govuk/components/skip-link/skip-link.mjs b/packages/govuk-frontend/src/govuk/components/skip-link/skip-link.mjs
index ec06ddd48e..392ee15472 100644
--- a/packages/govuk-frontend/src/govuk/components/skip-link/skip-link.mjs
+++ b/packages/govuk-frontend/src/govuk/components/skip-link/skip-link.mjs
@@ -2,6 +2,18 @@
  * Skip link component
  */
 export class SkipLink {
+  /** @private */
+  $module
+
+  /**
+   * @private
+   * @type {HTMLElement | null}
+   */
+  $linkedElement = null
+
+  /** @private */
+  linkedElementListener = false
+
   /**
    *
    * @param {Element} $module - HTML element to use for skip link
@@ -11,13 +23,7 @@ export class SkipLink {
       return this
     }
 
-    /** @private */
     this.$module = $module
-
-    /** @private */
-    this.$linkedElement = null
-
-    /** @private */
     this.linkedElementListener = false
   }
 
diff --git a/packages/govuk-frontend/src/govuk/components/tabs/tabs.mjs b/packages/govuk-frontend/src/govuk/components/tabs/tabs.mjs
index 5ff7fc800e..b59348144b 100644
--- a/packages/govuk-frontend/src/govuk/components/tabs/tabs.mjs
+++ b/packages/govuk-frontend/src/govuk/components/tabs/tabs.mjs
@@ -2,6 +2,30 @@
  * Tabs component
  */
 export class Tabs {
+  /** @private */
+  $module
+
+  /** @private */
+  $tabs
+
+  /** @private */
+  keys = { left: 37, right: 39, up: 38, down: 40 }
+
+  /** @private */
+  jsHiddenClass = 'govuk-tabs__panel--hidden'
+
+  /** @private */
+  changingHash = false
+
+  /** @private */
+  boundTabClick
+
+  /** @private */
+  boundTabKeydown
+
+  /** @private */
+  boundOnHashChange
+
   /**
    * @param {Element} $module - HTML element to use for tabs
    */
@@ -16,31 +40,13 @@ export class Tabs {
       return this
     }
 
-    /** @private */
     this.$module = $module
-
-    /** @private */
     this.$tabs = $tabs
 
-    /** @private */
-    this.keys = { left: 37, right: 39, up: 38, down: 40 }
-
-    /** @private */
-    this.jsHiddenClass = 'govuk-tabs__panel--hidden'
-
     // Save bounded functions to use when removing event listeners during teardown
-
-    /** @private */
     this.boundTabClick = this.onTabClick.bind(this)
-
-    /** @private */
     this.boundTabKeydown = this.onTabKeydown.bind(this)
-
-    /** @private */
     this.boundOnHashChange = this.onHashChange.bind(this)
-
-    /** @private */
-    this.changingHash = false
   }
 
   /**
diff --git a/packages/govuk-frontend/src/govuk/i18n.mjs b/packages/govuk-frontend/src/govuk/i18n.mjs
index 792ec08e17..eb922ee142 100644
--- a/packages/govuk-frontend/src/govuk/i18n.mjs
+++ b/packages/govuk-frontend/src/govuk/i18n.mjs
@@ -5,6 +5,9 @@
  * @private
  */
 export class I18n {
+  translations
+  locale
+
   /**
    * @param {{ [key: string]: unknown }} translations - Key-value pairs of the translation strings to use.
    * @param {object} [config] - Configuration options for the function.