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How to Optimize JavaScript for Search Engine

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JavaScript is one of the popular programming languages known for its excellent performance, aimed at enhancing the functionality and interactions within a website. JavaScript is a crucial component of many architectures used to build a website, as it makes websites more interactive and improves the user experience on the site.

Currently, there are numerous websites that use JavaScript as the foundation of their technology stack. Examples of popular JavaScript frameworks being utilized are ReactJS, VueJS, NuxtJS, NextJS, SvelteJS, and many more. Most of them leverage JavaScript to harness a wide range of technologies and facilities for building websites with the best user experience.


Figure 1. Several popular JavaScript frameworks currently

However, how can modern websites use JavaScript as their technological foundation and also target top positions in search results? How can the content on websites using JavaScript be visible to search engines?

The questions above are crucial when you truly use your website as a channel in digital marketing. Search Engine Optimization (SEO) becomes a vital step in these activities. The challenge is connecting a sophisticated JavaScript-based website with search engine optimization (SEO). The answer is JavaScript SEO. In this article, we will discuss the implementation of JavaScript SEO on your website.

What is JavaScript SEO?

JavaScript has played a crucial role as a highly popular programming language and technology in modern website development, particularly in enhancing interactivity and user experience. However, on the other hand, we need to pay attention to the right strategy for targeting top positions in search engine results pages (SERPs). 

A developer or webmaster needs to understand how a search engine like Google processes the JavaScript on their website. This helps them formulate the right strategies and address performance-related issues on their website.

JavaScript SEO is one of the branches of technical SEO that focuses on how a website using the JavaScript programming language and technology can be optimized to appear at the top positions and perform well in search engine results pages (SERPs). 


Figure 2. One of the websites that use JavaScript frameworks (ReactJS and NextJS)

The primary goal of JavaScript SEO is to enhance the visibility of websites built with JavaScript and implement the right optimization strategies. Here are some detailed explanations of the objectives of JavaScript SEO and why it's important for a website:

  • Improve Search Engine Visibility
    JavaScript SEO aims to ensure that websites built with JavaScript are properly indexed by search engines, making them visible to a wider audience. This involves making sure search engine crawlers can access and understand the content and structure of the website.
  • Enhance User Experience
    JavaScript is often used to create interactive and dynamic web experiences. Proper JavaScript SEO helps in optimizing these features while ensuring they don't compromise user experience,
  • Optimize Page Load Speed
    Websites using JavaScript can sometimes suffer from slow loading times, which can negatively impact SEO. JavaScript SEO strategies involve optimizing code and resources to improve page load speed, which is a ranking factor in search engines.
  • Mobile Friendliness
    With the rise of mobile users, ensuring that JavaScript-based websites are mobile-friendly is essential. JavaScript SEO includes strategies for responsive design and mobile optimization, as mobile-friendliness is a ranking factor for search engines.
  • Content Accessibility
    JavaScript-driven content can sometimes be challenging for search engines to crawl and index. JavaScript SEO focuses on making this content accessible to search engine bots, ensuring that all valuable content is properly ranked.

A developer or a webmaster need to pay attention to the aspects of JavaScript SEO in improving visibility and performance in the SERP. In the following discussion, we will delve deeper into effective optimization strategies for JavaScript SEO in search engines.

How Does GoogleBot Process JavaScript

After understanding the role and importance of JavaScript SEO for a website, it's time to discuss how the Google search engine processes a JavaScript-based website. Google utilizes Googlebot to crawl and index website pages. When Googlebot encounters a website page containing JavaScript, Google employs several processes to ensure that the page and its content are indexed correctly.

Figure 3. Google processes JavaScript until indexing occurs.


1. Crawling

The first step in search engine optimization involves the crawling process. Googlebot initially accesses the main HTML page and retrieves all necessary resources, including related JavaScript files. Unlike older crawler versions that only fetched HTML on a website page and considered the task complete, modern crawlers like Googlebot must adapt to websites utilizing JavaScript. 

While modern crawlers have the capability to execute JavaScript, limitations in resources may lead the crawler to skip the execution of JavaScript that is either too time-consuming or too complex. The consequence is that certain parts of the website pages may not be crawled effectively and, consequently, remain unindexed. 

This condition can pose a serious problem when a substantial amount of valuable content on the site is not indexed, potentially reducing the visibility and accessibility of that information.

2. Rendering HTML and JavaScript

After the crawling process is completed, Googlebot then renders the main HTML to gain an initial overview of the content and page structure. Googlebot utilizes the V8 rendering engine to execute JavaScript and fully render the page. This enables Googlebot to view the website page in a state similar to users running JavaScript in their browsers.

When the Javascript rendering process occurs, Google has important objectives within it. Google aims to track all URLs that need to be rendered and return them in a processed form. Furthermore, Google processes Javascript to see if there are any changes to the Document Object Model (DOM).

The rendering process becomes a crucial element for SEO because it affects how search engine bots index website pages and has a significant impact on user experience (UX). If all web pages are displayed effectively, and the navigation is easy, users are more likely to stay on the website.

In its implementation, there are three commonly used approaches in rendering a website, with details as follows:

1. Client Side Rendering (CSR)

In CSR, most of the page rendering process occurs on the client side (in the user's browser). The server sends a basic HTML document and JavaScript, which is executed by the browser to fetch and render additional content.

2. Server Side Rendering (SSR)

SSR involves the server sending fully rendered HTML to the client. The server processes the request, fetches the necessary data, and generates the HTML before sending it to the browser.

3. Static Site Generation (SSG)

SSG involves generating the entire website at build time, where HTML files are pre-built for each page. These pre-rendered pages are then served to the client without the need for server processing during runtime.

Here is a detailed comparison of each rendering approach:

AspectClient Side Rendering (CSR) Server Side Rendering (CSR) Static Site Generation (SSG)
Rendering LocationClient-side (Browser)Server-sidePre-build at building time
Initial Page LoadFaster, minimum HTML initiallyMay be slower due to server processingExtremely fast as pre-rendered HTML is served
SEOMay have challenges as some content is rendered after page loadGood for SEO as search engines can index fully rendered contentExcellent for SEO, as pages are pre-rendered and easily indexable
User InteractionMore dynamic and interactive user interfacesLimited interactivity during initial loadLess dynamic because changes may require a rebuild
Server LoadLighter server load as rendering happens on the client sideHigher server load as server generates HTML for each requestServer load is minimal during runtime
Performance on Slow DevicesSlower perceived load time on slower devicesFaster perceived load time on slower devicesExtremely fast load times on slower devices
Content UpdatesEasier to update content dynamically without reloading the entire pageRequires a server request for updates, but can be dynamic after initial loadRequires a rebuild for content updates
SuitabilityHighly dynamic and interactive applicationsContent with SEO considerations and where initial load performance is crucialContent with a focus on speed and SEO, less suitable for highly dynamic content


3. Page Indexing

After the page is fully rendered, Googlebot can index the content and add it to the Google index database to be displayed in search results. Initially, Googlebot focused on indexing HTML-based content on a website page. This means that if a website uses Javascript to render or load content, Googlebot may not be able to fully process and index that content.


Figure 4. Example of a website that has been indexed on the Google search results page with specific keywords.


However, over time, Googlebot has undergone improvements, and its ability to process JavaScript has advanced. Currently, Googlebot can execute and process JavaScript on web pages during the crawling process. This indicates that Googlebot can handle websites that use JavaScript to render or load content.

Although Googlebot can process JavaScript, there are several considerations to ensure that JavaScript content on a website page can be indexed effectively. Some of these considerations include:

  1. Execution Time
    Ensure that the execution of JavaScript does not take too long. If the JavaScript process is too complex or time-consuming, Googlebot may stop execution before all content is loaded.
  2. Code Readability
    Ensure that JavaScript code on a website page is well-written and readable. This can help Googlebot process content more efficiently.
  3. Check Through Googlebot Testing Tools
    After ensuring the above aspects, it is essential to conduct testing using Googlebot testing tools provided by Google. This is to verify that the JavaScript content on the web page can be accessed and processed effectively by Googlebot.

After understanding how Google processes a JavaScript-based website, the next step is to explore optimization strategies for creating a JavaScript-friendly website for SEO. This involves ensuring that Google can crawl, render, and index the website effectively on the Google search results page.

Making Your JavaScript More SEO-Friendly

SEO in the digital marketing sector has become a crucial element for the success of the business, considering that JavaScript is one of the most popular technologies for building websites. It is important for us to pay attention to how a website can be optimized in terms of SEO. 

Making JavaScript-based websites SEO-friendly requires several approaches to ensure that search engines can easily access and index the web pages. There are several approaches or tips that can be implemented to make JavaScript-based websites more SEO-friendly, which will be discussed in the following section.

1. Using Server-side Rendering (SSR) or Static Site Generation (SSG) Approaches for Rendering Websites

Server-side Rendering (SSR) or Static Site Generation (SSG) allows content to be generated on the server side before being sent to the user's browser. This helps search engines to view and index content without waiting for JavaScript processes to execute.

SSR produces HTML on the server side before sending it to the browser for display on the client. This makes it easier for search engines to index content because the main HTML content is already on the server side and has the potential to reduce page load time as HTML content can be prepared on the server side. 

Page loading is a crucial factor in search engine ranking, so this aspect needs to be carefully considered when targeting the top positions in search engine results.

SSG enables websites to generate pre-rendered static pages, which can be cached and distributed efficiently. This can significantly improve page loading times. SSG supports the use of Content Delivery Networks (CDN) effectively, allowing content to be cached and distributed on servers located close to users. This can enhance page loading times and overall website performance.

Both approaches support the use of SEO-friendly URLs, helping search engines recognize and index pages more effectively. While search engines can currently execute JavaScript, using SSR or SSG can ensure that the generated content is correctly indexed by search engine bots. 

With these approaches, faster page loading times and quickly accessible content can enhance user experience, influencing rankings in search engine results. Google consistently emphasizes the importance of UX in its ranking algorithm.

2. Using XML Sitemap

The use of an XML sitemap on a JavaScript-based website can help improve SEO by providing clear guidance to search engines regarding the structure and hierarchy of pages within the website. It is essential to ensure that the XML sitemap is generated on the server side before being sent to the browser or client. 

If the website utilizes Server-side Rendering (SSR) or server-side processes to create the sitemap, this will ensure that search engines can easily access and read the information in the sitemap.

Furthermore, it is crucial to ensure that the sitemap includes all pages within the website. This means the sitemap should cover all static, dynamic, or JavaScript-generated pages. Every page that you want to be indexed by search engines should be included or listed in the sitemap. 

Once the sitemap is defined, it is necessary to verify the sitemap in Google Search Console or any other search platform being used. This allows for monitoring the performance of the sitemap and gaining more insights into how search engines view the website. 

Regularly monitor the performance of the sitemap and if there are changes to the website structure or additions to content, be sure to update the sitemap and notify search engines.

3. Using Canonical URLs Correctly

The use of canonical URLs on JavaScript-based websites is crucial to ensure that search engines can understand the relationship between various versions of a page's URL and avoid content duplication issues. It is essential to ensure that all URLs for a specific page lead to the same canonical URL. This includes both URLs with or without www, as well as the use of the HTTP and HTTPS protocols if the website supports HTTPS.

Here is an example of the implementation of a canonical URL added to the HTML <head> tag:

<link rel="canonical" href="https://cmlabs.co/en-id">


The canonical URL tag above needs to be added to every page rendered by search engines, or each page should have a canonical URL corresponding to its URL version. If a website has pages divided into multiple sections using pagination, such as blogs, articles, or content pages, it is essential to ensure that each pagination page uses the canonical tag to refer to the main page. This will help consolidate the SEO value of each of these pages.

Ensuring the correct use of canonical URLs on JavaScript-based websites can help improve SEO and avoid duplicate content issues. With canonical URLs, it provides clear guidance to search engines about which page is considered the main version or the preferred version.

4. Optimizing Meta Information Tags (Title, Description, Robots, etc.)

The use of meta tags on JavaScript-based websites is crucial for optimizing SEO and providing essential information to search engines. There are several implementations of meta tags that can be applied, especially on websites utilizing JavaScript technology, including:

  1. Meta Title Tag.
  2. Meta Description Tag.
  3. Meta Robots Tag.
  4. Meta tags for Social Media (Opengraph and Twitter).

The use of meta tags is highly beneficial for search engines to detect the content presented on the website's pages, such as providing relevant keywords in the title tag and meta description tag. The most important aspect is to ensure that the meta robots tag allows for indexing and following, as shown in the code below:

<meta name="robots" content="index, follow">


The meta robots tag provides information and guidance to search engine bots about which pages of the website can be crawled and indexed.

5. Image Optimization

Image optimization is crucial for website performance, especially from an SEO perspective. Handling image loading requires special attention to improve the speed of page loading, particularly for websites aiming to rank at the top of search engine results. 

In addition to considering image loading, the image assets themselves need to be optimized. Here are several points that can be done to enhance image loading performance:

  1. Select an image format that is most suitable and supports SEO. For example, consider using the WebP format, as it provides good quality with smaller file sizes.
  2. Compress images to reduce file size without compromising quality. Use online compression tools or plugins to automate this process.
  3. Implement lazy loading to load images only when the page is accessed or scrolled down. Lazy loading can reduce initial page loading time and accelerate user experience when accessing the page.
  4. Include alternate text (alt text) for each image to provide a brief description of the image content. This helps search engines understand the content of the image and improves accessibility.
  5. Resize images according to the user's device screen resolution, known as responsive design. This prevents the loading of larger images than necessary.

6. Optimizing JavaScript Code Through Minification to Improve Page Speed

Optimizing JavaScript code through minification is a common practice to enhance page loading speed. Minification involves reducing the size of JavaScript files by removing unnecessary characters such as white spaces, comments, and newline characters, without altering its functionality. The goal is to reduce the page loading process without impacting indexing and ranking on search engine result pages.

There are several techniques for the minification process, including:

  1. When the website is about to be released to production, especially for JavaScript-based or framework-based websites, using a production build is crucial. Always use the minified version of JavaScript files generated during the production build for the released version of the website.
  2. Enable Gzip compression on the server to further reduce the size of minified JavaScript files during the transfer or upload process.
  3. Consider using a CDN to deliver minified JavaScript files. CDNs distribute files globally, reducing latency and speeding up loading times.
  4. Implement code splitting to load only the necessary JavaScript code for each page. This can significantly improve the initial page loading time.

Each optimization point mentioned above can be taken to make a JavaScript-based website SEO-friendly. With an SEO-friendly website, there is a greater potential to achieve a higher ranking on the SERP because all pages and content on the website can be easily crawled and indexed by search engines. This, in turn, makes it easier for users to find the website or specific pages.

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Rifqi Ardhian

Rifqi Ardhian

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