Today we will be creating a custom filter element based on data attributes in Vanilla JavaScript.

This means that we will have a filter mechanism select list and a list of elements with specific data-attributes on them.

The end result will look like this Codepen. (Choose an option to see the effect)

HTML Structure

We need a select list for the dropdown and a ul with random list ratings to get started.

It will look something like this:

<select id="rating">
  <option value="">Choose a rating</option>
  <option value="5">Minimum 5 stars</option>
  <option value="4">Minimum 4 stars</option>
  <option value="3">Minimum 3 stars</option>
  <option value="2">Minimum 2 stars</option>
  <option value="1">Minimum 1 stars</option>
</select>

<ul>
  <li data-rating="4"><span>item 1</span><i>rating 4</i></li>
  <li data-rating="2"><span>item 2</span><i>rating 2</i></li>
  <li data-rating="3"><span>item 3</span><i>rating 3</i></li>
  <li data-rating="1"><span>item 4</span><i>rating 1</i></li>
  <li data-rating="4"><span>item 5</span><i>rating 4</i></li>
  <li data-rating="1"><span>item 6</span><i>rating 1</i></li>
  <li data-rating="4"><span>item 7</span><i>rating 4</i></li>
  <li data-rating="4"><span>item 8</span><i>rating 4</i></li>
  <li data-rating="1"><span>item 9</span><i>rating 1</i></li>
  <li data-rating="5"><span>item 10</span><i>rating 5</i></li>
  <li data-rating="1"><span>item 11</span><i>rating 1</i></li>
  <li data-rating="2"><span>item 12</span><i>rating 2</i></li>
  <li data-rating="3"><span>item 13</span><i>rating 3</i></li>
  <li data-rating="1"><span>item 14</span><i>rating 1</i></li>
  <li data-rating="3"><span>item 15</span><i>rating 3</i></li>
  <li data-rating="5"><span>item 16</span><i>rating 5</i></li>
  <li data-rating="3"><span>item 17</span><i>rating 3</i></li>
  <li data-rating="5"><span>item 18</span><i>rating 5</i></li>
  <li data-rating="1"><span>item 19</span><i>rating 1</i></li>
  <li data-rating="2"><span>item 20</span><i>rating 2</i></li>
</ul>

For now let's get cracking in making this look a little bit better.

CSS Styling

select {
  margin: 50px auto;
  display: block;
}
ul {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr 1fr;
}
ul li {
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px dashed #ba3b46;
  flex-direction: column;
  height: 100px;
}
ul li.hidden {
  display: none;
}
ul span {
  font-weight: bold;
  margin-bottom: 20px;
}

We set some margin on the select element to space it out a little bit better. Then we convert the ul into a grid with four columns. And make the list items nicer, and a bit more spacious.

Vanilla JavaScript data-attribute filter

Now, let's enter the magic part, JavaScript.

First, we want to get the select item by its ID.

const rating = document.getElementById("rating");

The next thing we need is the list items. We use a querySelectorAll to get them.

const elements = document.querySelectorAll("li");

Let's add an eventListener to our select item. It will be called every time the value changes.

rating.addEventListener("change", function () {
    // Code here
});

Inside that, we need to get the value of the rating first.

let value = rating.value;
// 1,2,3,4, or 5

Then we want to loop over all our list items.

[...elements].forEach((element) => {
    // Code here
});

Within this block, we want to check if we have a value at all. Else we need to reset all the items.

Once we have a value, we must check if the rating is lower than the value.

if (value === "") {
    // Select empty option
  element.classList.remove("hidden");
} else {
    // Get the rating for this list item
  const rating = element.dataset.rating;
  // Check if the rating is lower than the value
  if (!rating || rating < value) {
      // Hide the element
    element.classList.add("hidden");
  } else {
      // Show the element
    element.classList.remove("hidden");
  }
}

The whole code will look like this:

const rating = document.getElementById("rating");
const elements = document.querySelectorAll("li");

rating.addEventListener("change", function () {
  let value = rating.value;
  [...elements].forEach((element) => {
    if (value === "") {
      element.classList.remove("hidden");
    } else {
      const rating = element.dataset.rating;
      if (!rating || rating < value) {
        element.classList.add("hidden");
      } else {
        element.classList.remove("hidden");
      }
    }
  });
});

There you go. We now have a vanilla JavaScript filter based on data-attributes.

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