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← DOM Manipulation with JavaScript
○The page is a tree○Exercise: follow the document reference○Load a script when the page is ready○Exercise: initialize a deferred script○Find one element by id or CSS selector○Exercise: select a notice and label○Compare DOM properties, HTML attributes, and node types○Exercise: inspect a room input and its nodes✦Module Quiz
○Find every match with querySelectorAll○Exercise: label every trail stop○Move from a child to its relatives○Exercise: trace a nested card○Check for missing elements and search within a card○Exercise: update only the chosen card○Compare a live HTMLCollection with a static NodeList○Exercise: safely expand a live collection✦Module Quiz
○Safe text and HTML○Exercise: render a safe notice○Read and change link attributes○Exercise: update an accessible link○Data attributes and conditional text○Exercise: announce session availability○Boolean attributes and DOM properties○Exercise: unlock a volunteer sign-up✦Module Quiz
○Add, remove, and check classes○Exercise: mark a favourite card○Toggle a panel accessibly●Exercise: toggle the help panel○Inline styles, classes, and hidden○Exercise: style and hide a notice○Change a CSS custom property from JavaScript○Exercise: change a workshop card accent✦Module Quiz
○Create and Append a Text Node○Exercise: Add a Reading List Item○Place Nodes Before and Between○Exercise: Order the Workshop Agenda○Remove, Replace, and Clear Safely○Exercise: Refresh a Museum Display○Clone a Card and Insert a Batch○Exercise: Clone Two Exhibit Cards✦Module Quiz
○Listen for Clicks with a Named Handler○Exercise: Check Library Hours○Event Target, Current Target, and Delegation○Exercise: Delegate Pantry Actions○Keyboard Events Without Trapping Keys○Exercise: Search the Recipe Box○Once, Remove, and Bubble○Exercise: Control Workshop Notifications✦Module Quiz
○Read a field while someone types○Build a live name preview○Handle submit without leaving the page○Validate a library request○Keep a selection in sync on change and reset○Sync a preference and its reset state○Read multiple checked values with FormData○Build a checkbox-based garden request✦Module Quiz
○Filter a list as someone types○Build a live trail finder○Toggle an accessible disclosure○Build a guide menu disclosure○Create and remove items with one delegated listener○Build a neighborhood task board○Sort a workshop table with accessible buttons○Build an accessible sortable resource table✦Module Quiz
○Read selectable cards and detail updates○Build directory cards and a selected profile○Trace live search and an empty state○Add live search to the community directory○Trace safe additions and delegated removal○Add and remove community directory cards✦Module Quiz
○Read and update a live itinerary○Build the workshop itinerary○Add a validated item through a form○Add a workshop session○Filter and remove live entries○Finish the workshop planner✦Module Quiz
○Fetch JSON and render safe text○Exercise: load recipe cards○Handle loading, empty, and failed responses○Exercise: handle alert states○Build a query with URLSearchParams○Exercise: search the catalog○Abort outdated requests○Exercise: keep the latest result✦Module Quiz
○Load a dashboard from an offline API fixture○Build an events dashboard○Query a dashboard with URLSearchParams○Add event search to the dashboard○Retry requests without stale results○Finish a resilient event dashboard✦Module Quiz

Exercise: toggle the help panel

The help button starts collapsed. Wire it so two clicks open then close its associated panel, updating visual and accessibility states together. This follows the Toggle a panel accessibly demo.

Recall and transfer

classList.toggle("is-open") adds the class if absent and removes it if present, returning the new boolean state. The button’s aria-expanded must be the string "true" when the panel is shown and "false" when hidden. aria-controls identifies the panel. Use the native hidden property to make a collapsed panel actually unavailable, not merely visually faded. Initialize all three states consistently.

Here is the same technique in a different setting; its selectors and data are not the answer to this exercise:

javascript
const menuButton = document.querySelector("#menu-button");
const menu = document.querySelector("#menu");
menuButton.addEventListener("click", () => {
  const open = menu.classList.toggle("is-open");
  menu.hidden = !open;
  menuButton.setAttribute("aria-expanded", String(open));
});

Recall the three linked states: is-open class, panel hidden, button aria-expanded. When open they are present, false, and "true"; when closed they are absent, true, and "false".

In this starter, index.html contains the targets, style.css holds the visual rules, and script.js is where you finish the behavior. Run the preview, make the change, then Submit to check each step. If nothing changes, first check the selector and whether the script is attached at the bottom of the page.

Your Task

  1. Click #help-toggle once to add is-open to #help-panel and show it by setting hidden to false.
  2. Keep aria-expanded on the button synchronized: true while open, then after the next click remove is-open, hide the panel, and set aria-expanded back to false.
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