DOM "Menu" Lab - Part 2

Intro

In the DOM Events lesson we saw how to run a function, i.e., an event listener, when an event, such as a click, was dispatched.

This lab continues where Part 1 left off and provides practice defining event listeners used to manipulate the DOM in response to user interaction. It also provides additional practice styling DOM elements dynamically using JavaScript.

This exercises from the lab are not deliverable.

However, if you'd like the challenge of completing them, please feel free to do so!

We will only be evaluating up to task 3.1

Setup

1. Continue to use project inside your labs folder you created in Part 1.
   This is what you should have thus far:

2. Insert an additional <nav> element within the <header> element in index.html:

   <header>
     <nav id="top-menu"></nav>
     <!-- Add the <nav> element below -->
     <nav id="sub-menu"></nav>
   </header>

   Note: Other than the above changes, DO NOT modify index.html in any way.

3. Add the following CSS to the bottom of style.css:

   header,
   #top-menu {
     position: relative;
   }
   
   #top-menu {
     z-index: 20;
   }
   
   #sub-menu {
     width: 100%;
     z-index: 10;
     transition: top 0.5s ease-out;
   }
   
   #sub-menu a:hover {
     background-color: var(--top-menu-bg);
   }
   
   nav a.active {
     background-color: var(--sub-menu-bg);
     color: var(--main-bg);
   }

   Note: Other than the above changes, DO NOT modify style.css in any way.

Tasks

Tasks 1.0 thru 3.1 were completed in Part 1.

Task 4.0

Select and cache the <nav id="sub-menu"> element in a variable named subMenuEl.

Task 4.1

Set the height subMenuEl element to be 100%.

Task 4.2

Set the background color of subMenuEl to the value stored in the --sub-menu-bg CSS custom property.

Task 4.3

Add the class of flex-around to the subMenuEl element.

Progress Check:

Task 4.4

Set the CSS position property of subMenuEl to the value of absolute.

Task 4.5

Set the CSS top property of subMenuEl to the value of 0.

Task 5.0

Update the menuLinks array in script.js to this:

var menuLinks = [
  { text: "about", href: "/about" },
  {
    text: "catalog",
    href: "#",
    subLinks: [
      { text: "all", href: "/catalog/all" },
      { text: "top selling", href: "/catalog/top" },
      { text: "search", href: "/catalog/search" },
    ],
  },
  {
    text: "orders",
    href: "#",
    subLinks: [
      { text: "new", href: "/orders/new" },
      { text: "pending", href: "/orders/pending" },
      { text: "history", href: "/orders/history" },
    ],
  },
  {
    text: "account",
    href: "#",
    subLinks: [
      { text: "profile", href: "/account/profile" },
      { text: "sign out", href: "/account/signout" },
    ],
  },
]

Task 5.1

Select and cache the all of the <a> elements inside of topMenuEl in a variable named topMenuLinks.

Declare a global showingSubMenu variable and initialize it to false;

Task 5.2

Attach a delegated 'click' event listener to topMenuEl.

The first line of code of the event listener function should call the event object's preventDefault() method.

The second line of code function should immediately return if the element clicked was not an <a> element.

console.log the content of the <a> to verify the handler is working.

Progress Check

Ensure that clicking ABOUT, CATALOG, etc. logs out about, catalog, etc. when a link is clicked.

Clicking anywhere other than on a link should do nothing.

Task 5.3

Next in the event listener, if the clicked <a> link has a class of active:

1. Remove the active class from the clicked <a> element.
2. Set the showingSubMenu to false.
3. Set the CSS top property of subMenuEl to 0.
4. return to exit the handler.

Task 5.4

Next, the event listener should remove a class name of active from each <a> element in topMenuLinks - whether the active class exists or not.

Hint: Removing a non-existent class from an element does not cause an error, so just remove it!

Task 5.5

Next, the event listener should add a class name of active to the <a> element that was clicked.

Task 5.6

Set showingSubMenu to true if the clicked <a> element's "link" object within menuLinks has a subLinks property (all do, except for the "link" object for ABOUT), otherwise, set it to false.

Hint: Saving the "link" object in a variable will come in handy for passing its subLinks array in Task 5.7

Progress Check

Clicking any of the links should make that link "active" and clear the others:

Clicking an "active" link should clear that link.

Task 5.7

Next in the event listener...

If showingSubMenu is true:

1. Call a buildSubMenu function passing to it the subLinks array for the clicked <a> element.
2. Set the CSS top property of subMenuEl to 100%.

Otherwise (showingSubMenu is false):

1. Set the CSS top property of subMenuEl to 0.

Task 5.8

Code the buildSubMenu function so that it:

1. Clears the contents of subMenuEl.
2. Iterates over the subLinks array passed as an argument; and for each "link" object:
   • Create an <a> element.
   • On the new element, add an href attribute with its value set to the href property of the "link" object.
   • Set the new element's content to the value of the text property of the "link" object.
   • Append the new element to the subMenuEl element.

Progress Check

Take the menu for a test drive!

Task 6.0

Attach a delegated 'click' event listener to subMenuEl.

The first line of code of the event listener function should call the event object's preventDefault() method.

The second line of code function should immediately return if the element clicked was not an <a> element.

console.log the content of the <a> to verify the handler is working.

Task 6.1

Next, the event listener should:

1. Set showingSubMenu to false.
2. Set the CSS top property of subMenuEl to 0.

Task 6.2

Remove the class name of active from each <a> element in topMenuLinks - whether the active class exists or not.

Task 6.3

Update the contents of mainEl to the contents of the <a> element, within an <h1>, clicked within subMenuEl.

Task 6.4

If the ABOUT link is clicked, an <h1>about</h1> should be displayed.

Congrats!