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Controlling classes with the HTML5 classList

From: JavaScript: Enhancing the DOM

Video: Controlling classes with the HTML5 classList

One peculiar aspect of the class attributes is that you can add not just one but as many classes as you want to any HTML element. So, modifying classes by using dot notation or even the set attribute method is not convenient if the element has more than one class. Thankfully, HTML5 adds a new property to the dom called a class list. This is a new object that is going to be added to all the nodes in your DOM. It allows you to do jQuery like modifications, class attributes. So for example, you can add, remove, or toggle classes.

Controlling classes with the HTML5 classList

One peculiar aspect of the class attributes is that you can add not just one but as many classes as you want to any HTML element. So, modifying classes by using dot notation or even the set attribute method is not convenient if the element has more than one class. Thankfully, HTML5 adds a new property to the dom called a class list. This is a new object that is going to be added to all the nodes in your DOM. It allows you to do jQuery like modifications, class attributes. So for example, you can add, remove, or toggle classes.

Unfortunately, it has pretty lousy support in Internet Explorer. So if we check caniuse.com, you could see that it's only supported in IE 10. As I mentioned, you can use the add method of classList to add a class without disrupting any existing classes in the document. You can use remove to remove a class without affecting any other existing classes. If you use the toggle method, it'll turn a class on or off. First time you call it, it'll add the class, the second time you call it, it'll remove it. You can also find out how many classes an element currently has, as well as whether or not an element contains a specific class.

So, let's take a look at this in a real document. So, here I am on the page for my website and I'm going to scroll down to this area right here and I'll pull up the console. And I'm going to hit the magnifying glass to access this first element. So, here we can see the path to that element. So, first I'm going to create a variable and assign it to this down element. I'm going to target an image in the div that has the artist list class.

Let's check that out my node and there it is. We've got the right node which is that element. And if I want to add a class, all I need to do is save my node.classlist, and then use the add method, and pass it a class. So, that added the class faded, you can see it right here in the breadcrumbs. And if I pull up my node again, you can see that it's there as well. So, if you use add again and add a different class, you can see that both classes are added.

You can see a red there in the breadcrumbs, and you can also see it if we call up the node. To remove a class, you use remove. Now, it only has the faded class. Let's go ahead and remove that one as well. If you use toggle, it'll turn a class on and off, so let's check that out. Let's toggle right here, and we'll call a class called hidden. First on my call it, it hides it, it returns also a true value.

And if I call it again, it shows it and it returns a false. You can also use contains to find out whether or not the element has a class, since we just took off the class hidden it returns false. This is a really handy way and super similar to the way jQuery lets you manage your class names. It's so convenient that it's worth using a Polyfill to give you access to it right now. So, you may want to check out this GitHub page for a good Polyfill that allows you to use this in older browsers.

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This video is part of

Image for JavaScript: Enhancing the DOM
JavaScript: Enhancing the DOM

36 video lessons · 7836 viewers

Ray Villalobos
Author

 
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  1. 2m 36s
    1. Welcome
      59s
    2. What you should know before watching this course
      50s
    3. Using the exercise files
      47s
  2. 24m 33s
    1. What is the Document Object Model (DOM)?
      3m 2s
    2. Navigating the DOM with developer tools
      8m 10s
    3. Testing JavaScript commands with the console
      5m 50s
    4. Communicating with the console through JavaScript
      7m 31s
  3. 31m 9s
    1. Selecting elements with getElementById
      4m 10s
    2. Choosing elements by HTML tag
      3m 20s
    3. Isolating elements by class name
      3m 12s
    4. Querying CSS to select elements
      4m 54s
    5. Working with named form elements
      3m 39s
    6. Understanding nodeType, nodeName, and nodeValue
      4m 30s
    7. Traversing up and down DOM nodes
      4m 40s
    8. Targeting node elements
      2m 44s
  4. 22m 25s
    1. Changing HTML attributes
      5m 25s
    2. Working with restricted attributes
      2m 49s
    3. Detecting data attributes
      3m 29s
    4. Controlling classes with the HTML5 classList
      3m 21s
    5. Targeting the attributes property
      1m 24s
    6. Using text content modifiers
      3m 42s
    7. Modifying elements as text
      2m 15s
  5. 14m 57s
    1. Creating and appending nodes
      4m 27s
    2. Controlling node insertions with insertBefore
      3m 17s
    3. Cloning and removing nodes
      4m 41s
    4. Replacing existing nodes
      2m 32s
  6. 26m 14s
    1. What we'll build
      2m 16s
    2. Adding a bubbling event listener
      4m 11s
    3. Creating and styling an overlay with JavaScript
      4m 39s
    4. Adding an image
      3m 48s
    5. Resizing images in the DOM
      2m 59s
    6. Centering an image
      2m 36s
    7. Handling clicks
      1m 29s
    8. Adjusting for scrolling
      1m 36s
    9. Detecting and adjusting for a window resize
      2m 40s
  7. 1m 49s
    1. Next steps
      1m 49s

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