Hiding DOM Elements by Class Name in JavaScript: A Comprehensive Guide

The ability to show and hide HTML elements is an essential skill for any front-end web developer working with JavaScript. One quick and easy way to target elements for hiding is by using their class name.

In this comprehensive guide, we will explore the ins and outs of hiding DOM elements by class name using native JavaScript.

Overview

Here is a quick overview of what we will cover:

• Selecting elements by class name using document.getElementsByClassName()
• Hiding a single element by setting display: none
• Hiding multiple elements with a loop
• Toggling visibility with a click handler
• Animating transitions for smooth hiding effects
• Supporting older browsers without class name selection

By the end, you‘ll have a complete JavaScript toolkit for hiding elements by class name for modern web development. Let‘s get started!

Selecting Elements by Class Name

The starting point for hiding anything on a page is being able to select it. While IDs are great for single elements, classes allow us to access multiple elements at once.

The document.getElementsByClassName() method returns a live HTMLCollection of found elements:

const elements = document.getElementsByClassName(classNames); 

We can supply one or more class names to match against, separated by spaces. This makes getElementsByClassName() more flexible than getElementById().

Consider this page structure:

<div class="box blue">...</div>
<div class="box red">...</div>
<div class="box green">...</div>

To get all elements with the box class, we would use:

const boxes = document.getElementsByClassName(‘box‘);

Now boxes contains all .box elements, allowing us to manipulate them together.

Hiding a Single Element

The easiest case is hiding one specific element by class name.

To do this, we:

1. Select the element
2. Set display: none on its style

Here is an example:

// Get first .box element
const box = document.getElementsByClassName(‘box‘)[0]; 

// Hide it
box.style.display = ‘none‘;

And just like that, our first box is hidden!

The key is setting display: none, which removes the element from the normal layout flow. Other properties like visibility: hidden only make it invisible but still take up space.

Hiding Multiple Elements

Hiding one element at a time is great, but we can easily hide all elements with a given class using a simple loop:

// Get all .box elements
const boxes = document.getElementsByClassName(‘box‘);

// Loop over them and hide
for (let i = 0; i < boxes.length; i++) {
  boxes[i].style.display = ‘none‘; 
}

And now all boxes are gone!

This uses a standard for loop to iterate over the boxes HTMLCollection and hide each one individually.

We could combine this with an event listener to hide boxes on command:

document.getElementById(‘hide-boxes‘).addEventListener(‘click‘, () => {

  // Hide all boxes
  const boxes = document.getElementsByClassName(‘box‘);

  for (let i = 0; i < boxes.length; i++) {
    boxes[i].style.display = ‘none‘;
  }

});

Now clicking our #hide-boxes button elegantly hides every box on the page.

Toggling Visibility

Along with hiding content, we often want the ability to show it again later. This is where the concept of toggling comes into play.

By attaching our box-hiding logic to a click handler, we can flip their visibility back and forth:

let hidden = false;

document.getElementById(‘toggle-boxes‘).addEventListener(‘click‘, () => {

  // Get box elements
  const boxes = document.getElementsByClassName(‘box‘);

  if (hidden) {
    // Show boxes
    for (let i = 0; i < boxes.length; i++) {
      boxes[i].style.display = ‘block‘; 
    }

    hidden = false;

  } else {
    // Hide boxes 
    for (let i = 0; i < boxes.length; i++) {
      boxes[i].style.display = ‘none‘;
    }

    hidden = true;
  }

});

Clicking now intelligently toggles between hiding and showing to create an interactive effect.

Animating Hidden Elements

Hiding elements instantly can feel abrupt for users. A better approach is animating changes for smoother transitions:

.box {
  transition: all 0.3s ease-out;
}

This CSS sets up transition timing on all property changes.

We modify our JavaScript to:

// Loop over boxes
for (let i = 0; i < boxes.length; i++) {

  // Hide each box over 0.3s
  boxes[i].style.opacity = ‘0‘;
  boxes[i].style.transform = ‘scale(0.9)‘;

  setTimeout(() => {
    boxes[i].style.display = ‘none‘;
  }, 300);

} 

First, we animate opacity and transform to fade/shrink each box visually.

After the transition period via setTimeout(), we set display: none to officially remove from layout.

The result? Smooth animated interactions instead of jarring jumps!

Cross-Browser Compatibility

getElementsByClassName() offers handy class lookup, but isn‘t supported in legacy browsers like IE8.

We can polyfill this functionality with a helper function:

function getElementsByClassName(className) {

  const elements = document.querySelectorAll(‘.‘ + className);

  return elements;
}

const boxes = getElementsByClassName(‘box‘);

This uses querySelectorAll() instead, which finds elements purely by CSS selector.

As long as we pass a valid selector like .box, we get a nice array of elements matching .box as needed.

We can then loop over hiding with the same logic as before!

Recap

Let‘s review the key topics around hiding elements by class name:

• Select elements with getElementsByClassName(), falling back to querySelectorAll()
• Hide a single element by setting display: none
• Use a loop to hide multiple elements at once
• Toggle visibility on user events for interactivity
• Animate transitions with CSS and setTimeout()
• Support older browsers lacking class functions

This covers all the basics – you now have a professional-grade solution for hiding DOM elements by targeting class name with JavaScript!

More Resources

To dive deeper, explore these additional resources:

• MDN Web Docs on Document.getElementsByClassName()
• Hiding and Showing Content with CSS
• Create Slide Out Boxes with JavaScript

I hope you found this guide helpful! Let me know if you have any other questions. Happy coding!