Great user interface (UI) design elicits an emotive response, merging the gap between human thoughts and your application. An essential part of this UX fruition can be chalked down to UI performance and responsiveness. In this post, let’s take a deep dive into modern techniques, code examples, and prominent pitfalls for shaping high-performant and responsive UIs.

A Performant and Responsive UI - Why it Matters?

As Google Developers states,

“Performance plays a significant role in the success of any online venture.”

Performance is understood as the speed of your GUI, how quickly it loads and how smoothly it responds to user interaction. Responsiveness here refers to the application’s ability to adjust across different device sizes and screen layouts. A well-designed UI that’s sluggish offers the same user experience as an ugly, albeit fast UI.

Modern Techniques for Performance and Responsiveness

1. Code Splitting

JavaScript’s size contributes significantly to your page load time. Code Splitting assists you in managing code debt by dividing your code into smaller pieces or ‘chunks’, loading only what’s required on-demand.

Libraries like Split.js allow dividing UI elements into adjustable, resizable panes, allowing you to split your code into multiple bundles and then loading a bundle on demand, as detailed in this public GitHub repository.

2. Opt for efficient re-rendering

For performance gains, try adopting shallow rendering with libraries like ‘Enzyme’. Shallow rendering enables you to test your components as a unit, and indirectly ensure that child components aren’t unintentionally affected by parent component re-renders.

import { shallow } from 'enzyme';

const element = shallow(<MyComponent />);

Check more examples here.

3. Responsive Images

Images often consume significant bandwidth. Thankfully, HTML5 introduced tags like picture and source, allowing multiple image versions based on viewport dimensions.

<source srcset="/img/hero-desktop.jpg" media="(min-width: 1000px)">
<source srcset="/img/hero-tablet.jpg" media="(min-width: 600px)">
<img src="/img/hero-mobile.jpg" alt="...">

The browser loads the appropriate image source based on its own device-width.

4. Adaptive Components

Creating adaptive components can enhance UI responsiveness. For instance, in CSS Grid layouts the repeat() function along with directive auto-fill can dynamically present more items per row as screen space allows, thus creating an adaptable viewing experience.

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));

Read more from Sara Soueidan’s comprehensive guide.

Gotchas and Pitfalls

While striving to deliver a performant, responsive UI, some common pitfalls include:

  1. Non-optimized assets: Big images, unminified JS, and surplus CSS significantly hamper load time. Use optimizers and minifiers.

  2. Ignoring browser caching: Browser caching temporarily stores site data, reducing server load, and ensuring faster loads on revisits.

  3. Lack of performance testing: Emulate average network and hardware conditions, do not design for ideal situations.

  4. Non-responsive breakpoints: Use breakpoints not merely based on devices but content. Josh Brewer stated it well, “the content is like water”, thus your design should adapt to its container.

  5. Overlooking accessibility: A responsive, performant site must be accessible for every user. Implement ARIA roles and test your site with tools like Google’s Lighthouse.

UI’s performance and responsiveness are substantial to the overall user experience. They ensure your application outputs standout design while being pleasingly fast and accessible. In the epoch where users' attention spans are increasingly shrinking, neglecting these aspects might cost you users.

Remember, your UI may be a user’s first form of interaction with your brand. Consequently, ensuring it’s performant and responsive is investing in the first cube of user trust and satisfaction.