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Filtering Data Client-Side: Comparing CSS, jQuery, and React

September 24th, 2019

Say you have a list of 100 names:

<ul>
  <li>Randy Hilpert</li>
  <li>Peggie Jacobi</li>
  <li>Ethelyn Nolan Sr.</li> 
  <!-- and then some -->
</ul>

…or file names, or phone numbers, or whatever. And you want to filter them client-side, meaning you aren’t making a server-side request to search through data and return results. You just want to type “rand” and have it filter the list to include “Randy Hilpert” and “Danika Randall” because they both have that string of characters in them. Everything else isn’t included in the results.

Let’s look at how we might do that with different technologies.

CSS can sorta do it, with a little help.

CSS can’t select things based on the content they contain, but it can select on attributes and the values of those attributes. So let’s move the names into attributes as well.

<ul>
  <li data-name="Randy Hilpert">Randy Hilpert</li>
  <li data-name="Peggie Jacobi">Peggie Jacobi</li>
  <li data-name="Ethelyn Nolan Sr.">Ethelyn Nolan Sr.</li> 
  ...
</ul>

Now to filter that list for names that contain “rand”, it’s very easy:

li {
  display: none;
}
li[data-name*="rand" i] {
  display: list-item;
}

Note the i on Line 4. That means “case insensitive” which is very useful here.

To make this work dynamically with a filter <input>, we’ll need to get JavaScript involved to not only react to the filter being typed in, but generate CSS that matches what is being searched.

Say we have a <style> block sitting on the page:

<style id="cssFilter">
  /* dynamically generated CSS will be put in here */
</style>

We can watch for changes on our filter input and generate that CSS:

filterElement.addEventListener("input", e => {
  let filter = e.target.value;
  let css = filter ? `
    li {
      display: none;
    }
    li[data-name*="${filter}" i] {
      display: list-item;
    }
  ` : ``;
  window.cssFilter.innerHTML = css;
});

Note that we’re emptying out the style block when the filter is empty, so all results show.

See the Pen Filtering Technique: CSS by Chris Coyier (@chriscoyier) on CodePen.

I’ll admit it’s a smidge weird to leverage CSS for this, but Tim Carry once took it way further if you’re interested in the concept.

jQuery makes it even easier.

Since we need JavaScript anyway, perhaps jQuery is an acceptable tool. There are two notable changes here:

  • jQuery can select items based on the content they contain. It has a selector API just for this. We don’t need the extra attribute anymore.
  • This keeps all the filtering to a single technology.

We still watch the input for typing, then if we have a filter term, we hide all the list items and reveal the ones that contain our filter term. Otherwise, we reveal them all again:

const listItems = $("li");

$("#filter").on("input", function() {
  let filter = $(this).val();
  if (filter) {
    listItems.hide();
    $(`li:contains('${filter}')`).show();
  } else {
    listItems.show();
  }
});

It’s takes more fiddling to make the filter case-insensitive than CSS does, but we can do it by overriding the default method:

jQuery.expr[':'].contains = function(a, i, m) {
  return jQuery(a).text().toUpperCase()
      .indexOf(m[3].toUpperCase()) >= 0;
};

See the Pen Filtering Technique: jQuery by Chris Coyier (@chriscoyier) on CodePen.

React can do it with state and rendering only what it needs.

There is no one-true-way to do this in React, but I would think it’s React-y to keep the list of names as data (like an Array), map over them, and only render what you need. Changes in the input filter the data itself and React re-renders as necessary.

If we have an names = [array, of, names], we can filter it pretty easily:

filteredNames = names.filter(name => {
  return name.includes(filter);
});

This time, case sensitivity can be done like this:

filteredNames = names.filter(name => {
  return name.toUpperCase().includes(filter.toUpperCase());
});

Then we’d do the typical .map() thing in JSX to loop over our array and output the names.

See the Pen Filtering Technique: React by Chris Coyier (@chriscoyier) on CodePen.

I don’t have any particular preference

This isn’t the kind of thing you choose technology for. You do it in whatever technology you already have. I also don’t think anyone approach is particularly heavier than the rest in terms of technical debt.