Code Fix #3: Toggling Classes with querySelectorAll

Welcome back! In this article, I'll be going over toggling classes with querySelectorAll.

Background

The person was given the HTML and CSS below:

<!-- index.html -->
<ul>
  <li>Hello</li>
  <li class="highlight">Hello</li>
  <li>Hello</li>
  <li class="highlight">Hello</li>
  <li>Hello</li>
  <li class="highlight">Hello</li>
</ul>

/* styles.css */
.highlight {
  background-color: #d09cd9;
}

Ouput

The Task

The task was to toggle the class "highlight" among the <li> elements to change the output to this:

The Problem

This person had the code below, which wasn't getting the expected results:

const items = document.querySelector("li");

for (let item of items) {
    item.classList.toggle("hidden");
}

Why It Doesn't Work

This is thankfully a simple fix!

The querySelector method returns only the first element that matches the specified selector.

const items = document.querySelector("li");
console.log(items); // <li>Hello</li>

Instead, querySelectorAll should be used, which grabs all elements that match and puts them into a NodeList - a collection of nodes in an array.

const items = document.querySelectorAll("li");
console.log(items); // NodeList (6), [<li>Hello</li>, <li class="highlight">Hello</li>...]

The Solution

There are different ways you can code this:

//Option 1 with a for...of loop
const items = document.querySelectorAll("li");

for (let item of items) {
    item.classList.toggle("highlight");
}

If you're not a fan of for...of loops, you'll get the same result with a regular for loop:

// Option 2 with a for loop
const items = document.querySelectorAll("li");

for (let i = 0; i <= items.length; i++) {
    items[i].classList.toggle("highlight");
}

Lastly, you can use the forEach method for arrays:

// Option 3 with forEach
const items = document.querySelectorAll("li");

items.forEach(item => item.classList.toggle("highlight");

I hope this helped. Feel free to check out the CodePen!

Do you have another way of doing this? Let me know in the comments!