Performance optimization of frontend applications plays an important role in the application architecture. A higher-performing application will ensure an increase in user retention, improved user experience, and higher conversion rates.
According to Google, 53% of mobile phone users leave the site if it takes more than 3 seconds to load. At the same time, more than half of the pages tested are heavy in terms of bandwidth it utilizes to download the required assets. Don’t forget your frontend application performance directly affects its search ranking and conversion rates.
We use the Vue JS framework for our frontend applications. The challenge we had with our frontend application was with the landing page, which was taking around 3.8 secs to load with 4.2 MB of resources to be downloaded. As the response time was quite high, it was challenging to retain the users.
This article would share some of the implementation changes which we did to improve the performance of our frontend application.
Image compression is really important when optimizing frontend applications. Lighter images get downloaded faster and load with less time as compared to larger images. By compressing the images, we can make our site much lighter and hence results in slower page load times.
WebP is a modern image format that provides superior lossless and lossy compression for images on the web. Using WebP, webmasters and web developers can create smaller, richer images that make the web faster.
WebP lossless images are 26% smaller in size compared to PNGs. WebP lossy images are 25–34% smaller than comparable JPEG images at equivalent SSIM quality index.
WebP is supported by Chrome, Firefox, Edge, and Safari from version 14 and above. Please feel free to read more about WebP.
It is evident that download time has reduced on applying webp compression.
Synchronous Components Loading
Synchronous components loading is the process of loading the components with the import statement which is the basic way of loading the component.
Components loaded with a static import statement will be added to the existing application bundle. If code splitting is not used then the application core will become huge in size, hence affects the overall performance of the application.
The below code snippet is an example of static component loading of store and locale components.
import store from '@common/src/store' import locale from '@common/src/util/locale'
Asynchronous Components Loading
Asynchronous components loading is the process where we load chunks of our application in a lazy manner. It ensures that components are only loaded when they are needed.
Lazy loading ensures that the bundle is split and serves only the needed parts so users are not waiting to download and parse the code that will not be used.
In the below code snippet, the image of YouTube is loaded asynchronously when it’s needed.
<template> <lazy-image :lazy-src="require('@/assets/images/icon/youtube.png')" alt="YouTube" draggable="false" /> </template> <template> <img v-if="lazySrc" ref="lazy" :src="defaultImage" :data-src="lazySrc" :alt="alt" class="lazyImage" @error="handleError"> <img v-else :src="defaultImage"> </template>
Dynamic Components Loading
To dynamically load a component, we declare a const and append an arrow function followed by the default static import statement.
We can also add a web pack magic comment. The comment will tell webpack to assign our chunk the name we provided otherwise webpack will auto-generate a name by itself.
const MainBanner = () => import(/* webpackChunkName: "c-main-banner" */ '@/components/MainBanner')
If we go to our developer tools and open the Network tab we can see that our chunk has been assigned the name we provided in the webpack’s chunk name comment.
According to Dev Mozilla, code splitting is the process of splitting the application code into various bundles or components which can then be loaded on-demand or in parallel.
We don’t have much control in terms of third party libraries downloads as they are required for our application to work. At least we should make sure our code is split into multiple smaller files. The features required at page load can be downloaded quickly with smaller files and with additional scripts being lazy-loaded after the page or application is interactive, thus improves the performance.
we have seen some of the frontend developers’ arguments, it will increase the number of files but the code remains the same. We completely agree with them but the main thing over here is the amount of code needed during the initial load can be reduced.
Code splitting is a feature supported by bundlers like Webpack and Browserify which can create multiple bundles that can be dynamically loaded at runtime or we can do the old school way where we can split the code required for individual vue files can be separated and loaded on demand.
Basically, third-party requests can slow down page loads for several reasons like slow networks, long DNS lookups, multiple redirects, slow servers, poor performing CDN, etc.
As third-party resources (e.g., Facebook or Twitter, or MoEngage) do not originate from your domain, their behavior is sometimes difficult to predict and they may negatively affect page experience for your users.
Using preconnect helps the browser prioritize important third-party connections and speeds up your page load as third-party requests may take a long time to process. Establishing early connections to these third-party origins by using a resource hint like preconnect can help reduce the time delay usually associated with these requests.
preconnect is useful when you know the origin of the third-party request but don’t know what the actual resource itself is. It informs your browser that the page intends to connect to another origin and that you would like this process to start as soon as possible. The browser closes any connection that isn’t used within 15 seconds, so preconnect should only be used for the most critical third-party domains.
As a part of best practices, we need to make sure we don’t have any commented code in JS or CSS files. It’s commented because we don’t want to use them, so better get rid of them as the commented code contributes to an increase in the size of the file.
As part of frontend application development, we might use some CSS frameworks but you will only use a small set of the framework styles, and a lot of unused CSS styles will be included.
According to PurgeCSS, it’s a tool to remove unused CSS. It can be part of your development workflow. PurgeCSS analyzes your content and your CSS files then it matches the selectors used in your files with the ones in your content files. It removes unused selectors from your CSS, resulting in smaller CSS files.
Also while importing anything from 3rd party libraries to run the application, we can use the tree-shaking mechanism that can avoid the unused CSS and JS code included in our 3rd party bundles. To analyze this kind of unwanted JS and CSS items from 3rd party libraries there is a tool called webpack bundle analyzer.
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