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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

Compare a live HTMLCollection with a static NodeList

The market board used querySelectorAll to capture a static NodeList. At a pond survey, getElementsByClassName("sighting") instead returns a live HTMLCollection: its membership changes as matching elements enter or leave the document. These two lists are taken before a new sighting is added.

javascript
const live = document.getElementsByClassName("sighting");
const staticList = document.querySelectorAll(".sighting");
const original = Array.from(live);
original.forEach((entry) => {
  entry.textContent += " — checked";
});
const next = document.createElement("li");
next.className = "sighting";
next.textContent = "Heron — new";
document.getElementById("sightings").appendChild(next);
document.getElementById("live-count").textContent = live.length;
document.getElementById("static-count").textContent = staticList.length;

createElement("li") makes a new list item in memory; setting className and textContent prepares it, and appendChild(next) puts it in the list. Node creation gets a fuller treatment later; here it makes the two collection types visibly diverge. Run: the original two sightings gain — checked; the new heron stays — new. The live collection now contains three, but the earlier static NodeList still contains two. This is a difference in membership, not whether edits to existing nodes are visible: both lists still refer to the original elements. We convert the live collection to an array before iterating so adding matching nodes cannot extend the loop unexpectedly. Unlike a NodeList, an HTMLCollection does not have forEach directly. Try changing next.className to "other" and run again; the live count then stays two. Restore it for the next exercise.

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