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Isolating elements by class name

From: JavaScript: Enhancing the DOM

Video: Isolating elements by class name

So far, we've looked at picking elements by ID and tag name. So, you're probably thinking that you can also pick elements by class name, and you would be right, sort of. The getElementsByClassName function is a bit of a new addition. Of course, it does that you select that elements with a specific class, but because it is a newer selector it is incompatible with older browsers. Whenever you have a question about whether a browser has support for a method, you should check out a couple of web pages. This one right here called caniuse.com is a really good resource. So, if you scroll down you can see that this method has support in pretty much every modern browser but not older versions of IE. Another page you should check out is the W3C.ompatibilty.

Isolating elements by class name

So far, we've looked at picking elements by ID and tag name. So, you're probably thinking that you can also pick elements by class name, and you would be right, sort of. The getElementsByClassName function is a bit of a new addition. Of course, it does that you select that elements with a specific class, but because it is a newer selector it is incompatible with older browsers. Whenever you have a question about whether a browser has support for a method, you should check out a couple of web pages. This one right here called caniuse.com is a really good resource. So, if you scroll down you can see that this method has support in pretty much every modern browser but not older versions of IE. Another page you should check out is the W3C.ompatibilty.

If you scroll down on this page see you can get to the same information on the get element by class name method. Now, I'm using a pretty modern browser here this is a late version of Chrome so you shouldn't have a problem with this method. So, I'm going to go to my website I'll click on the Artists section this time. So, this page just has a list of artists right here. And I'm going to break into the developer tools by hitting Cmd option I that would Ctrl+Alt+I on the PC and then hitting the Escape key. And then I can type in document. (SOUND) getElements, remember it's plural, ByClassName. Then, I can type in the class name that I'm looking for. So if you don't know the class name, you can hit this magnifying glass. And just click on any one of these images, and it gives you the whole path to that element.

So, this element has a class of artists, so I'll type that in. And it returns every single artist on this page. Now if you have to many items match in a class, say that you had two separate lists of artists. You can get more specific by first finding the element with the ID. So you could do something like document, get element by ID, and then type it in first the ID. So, we know that looking at the breadcrumbs we can see that this has an ID of artist list, and then we can do get elements by class name.

So, this takes us to the same place but if you had multiple lists on the same page with the same class, this might be a better target. So as I mentioned earlier, this function is not supported on IE or earlier. Because of this a lot of people have written their own implementation usually called a polyfill of the get elements by class name method. That's so that they can support older browsers. If you want to check some of those out you may want to go to this URL right here this page is put together by John Resig creator of jQuery.

And it compares the different methods that people use to support older browsers, and get elements by class name. Frankly, if you want to support really old browsers. You may want to look into a library like jQuery. It has much better class selectors, and a whole lot of other goodies. I'm really surprised that this wasn't a function from the beginning in JavaScript. It seems like a no brainer, especially if you already have a version that gets elements by ID. It means that whether or not you use this function depends on what browsers you want to support in your applications.

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This video is part of

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

36 video lessons · 7634 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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