It’s unique because it can run directly in your browser, not just on a server.
Think of these coding languages as the components of a house:
- HTML is the foundation of the house. It provides the basic layout, structure, and content of a website.
- CSS is the interior design. It provides design, fonts, colors, effects, and other visual elements.
Netscape sought to develop a scripting language that could help make early versions of the World Wide Web more dynamic.
Its growing popularity has facilitated the development of libraries and frameworks, dedicated JS engines such as V8 (which powers Chrome), and server-side environments.
Libraries vs. Frameworks
Libraries lead to faster development because developers don’t need to write every line of code.
Frameworks are collections of libraries.
Think of libraries as tools. And frameworks as fully loaded toolboxes.
Although a library can provide code for a specific function on your website, a framework can provide all the code you need to build the website.
Developers use JS to add animations, pop-up windows, search bars, buttons, audio and video, chat widgets, and other interactive elements to a webpage.
You can also use JS to provide real-time updates to a page without reloading it.
Web-Based Games and Applications
Because it runs directly in the browser, JS allows users to play games and run applications without downloading additional software.
This results in lots of dynamic, interactive utility.
Other languages, such as C and C++, use ahead-of-time compilation. This means the language is compiled into simpler machine code before it’s executed.
Especially for simpler functions and processes, ahead-of-time compilation can be slower.
Even real-time communication applications, such as Google Meet, Zoom, and Slack, can function in-browser because of JS.
Server-side programming refers to code that runs on a web server to handle requests from clients (such as web browsers) and return responses.
This allows developers to build fast and scalable web applications, interact with databases, build application programming interfaces (APIs), and facilitate real-time communication.
For example, server-side programming is what allows for dynamic pages like Facebook’s newsfeed.
If each post, story, and status update were built on individual static pages, it would be extremely inefficient and require millions of pages.
The same concept applies to ecommerce websites like Amazon.
Mobile App Development
You can use JS libraries such as TensorFlow.js and Brain.js to build and train machine learning models for sentiment analysis and recommendation systems.
Other libraries can be used to process and analyze human language for natural language processing (NLP) systems.
It’s an Interpreted Language
This means it can be executed directly in a browser.
Other languages, like C, C++, and Java, are compiled languages and need to be translated into machine code before they can be executed.
It Uses Dynamic Typing
Dynamic typing means variable types are associated with runtime values, not named or declared fields.
This allows developers to write code faster, as they don’t have to worry about specifying variable types.
For example, a developer could assign the variable “a” the value of 100. The compiler will infer at runtime that “a” represents an integer.
However, this also means variable types could be misinterpreted as they are run. This can cause bugs and errors.
It’s Primarily Used in Client-Side Execution
Other major languages, such as PHP and Ruby, are primarily used server-side.
It’s supported by all major browsers.
It can be used both client-side and server-side.
And it can be used to develop websites, mobile apps, and software.
- It’s relatively easy to learn and use
- It can be used for client-side and server-side, front end and back end
- It provides dynamism and interactivity on websites
- Due to its popularity, there are many helpful resources available
- It runs on multiple platforms and devices
- It allows for cross-platform compatibility
- It’s supported by all major web browsers
- There are many libraries, frameworks, and APIs available to facilitate tasks
- It’s fast for client-side and simple tasks
- It works well in concert with other programming languages
- It can be slow for computationally heavy tasks
- It comes with inherent security concerns due to access to the client's browser
- Bugs can be difficult to find and resolve
- Crawlers may have trouble crawling and analyzing JS content
- Browsers interpret JS differently, which creates varying experiences
But when you use JS appropriately and in moderation, the benefits can counter the negative effects on performance.
The more code and scripts on your page, the worse the page will perform.
Your user’s browser has to download, parse, and execute each JS script in order of HTML appearance.
This includes scripts such as Google Analytics, Google Tag Manager, Google Ads, ImpactHero, and even web fonts.
Visual components such as image carousels and video embeds can also increase page loading time.
Complex themes and plugins will also negatively affect your site performance.
If important on-page elements, such as your content, load too slowly, it can negatively affect the user experience and cause them to bounce.
This can hurt your SEO efforts, your traffic, and, ultimately, your business.
Additionally, not everyone has high-performance devices and high-speed internet connections.
Although pages may load quickly on your computer, they may not on your users’ devices.
Adding dynamism and interactivity to your webpages will improve user experience, but adding too much can have the opposite effect.
People don’t like waiting. Especially on the internet.
If your site takes too long to load, users may be frustrated, hit the back button, and leave for your competitors’ sites.
This is bad for business. And bad for your search ranking, too.
Core Web Vitals
Core Web Vitals are metrics Google developed to analyze a website’s performance and the experience it provides.
Tools like Semrush’s Site Audit and Google Search Console can identify JS-related issues on your webpages.
The JS code must be enclosed in script tags, as shown below:
This is useful when you want to add the same code to multiple pages.
It’s also useful when you have lots of code to add to the page.
Regardless of the method you choose, you must ensure the code is enclosed in script tags on every page you want it to work on.
We recommend the following resources and tutorials to get started:
However, to make the most of it, you must ensure your code is as polished as possible.
Removing these lines and spaces can improve page load time without sacrificing content or functionality.
First Input Delay
First Input Delay (FID) refers to the time it takes for the browser to respond after a user first interacts with your website (e.g., clicks a link).
FID is one of the most important Core Web Vitals. And it can affect your search engine ranking.
Luckily, the Site Audit tool can identify First Input Delay problems and what’s causing them.
Balance Is Key
But it can also easily cause site performance issues.
Balance is key.
Strike a balance between user experience and performance to optimize your website.
Fortunately, the powerful tools available in Semrush's Site Audit can help you find this balance and solve issues.
Other examples include drop-down menus, interactive calendars, audio and video embeds, interactive maps, image carousels, and display ads.