Tips On How To Speed Up Your Javascript Code

by Sunny Hoi


JavaScript comprises one of the three main programming languages on a webpage. Even though it’s not a requisite, the majority of sites insist on JavaScript for functionality. You may possess the ideal server equipment available on the market today, but poor JavaScript code may pose a bottleneck and slow down your site’s load times.

Below are some tips to speed up your website with relatively simple JavaScript tweaks:

1. Manipulation Of Elements Prior To Adding Them To The DOM

The DOM is interconnected to each element such as HTML and its data printed in the web browser. It’s habitual for web developers to get back values from the DOM and modify them based on user input. It can appear monotonous, but manipulating values subsequent to printing them to the DOM consumes more time than doing so with DOM elements stripped out.

For example, if you hold some content that you wish to print to a div element, use JavaScript to create changes to the content as a string in addition to printing the string to the element. You diminish the necessity for the JavaScript engine to process HTML while you handle variable content.

2. Minifying Your JavaScript Files

While you create JavaScript files, formatting assists you to read code and comprehend its rationale. Any person who has a fundamental grasp of programming understands the significance of formatting syntax to make it simpler to read. Nonetheless, your web server doesn’t require these format characters to process files. You may decrease the size of JavaScript files by minifying them.

Minifying occurs when one begins stripping special formatting characters like tabs and extra spaces out of coding files. The file size decreased by numerous bytes preserves your users time downloading script. This is step is indispensable for websites that retain numerous external scripts that have to load for the site to function.

3. Position Script Includes At The Bottom Of Your HTML Pages

As a web browser loads a page, it loads it starting from the top to bottom. It’s common for web developers to put CSS and JS links in the head section of HTML pages. This particular section is typically set at the top of the page following the opening HTML tag. This indicates that the browser initially loads JS and CSS files, then proceeds to load the body tag content.

The mere seconds it takes for JS and CSS files to load obviously makes a noticeable difference in user engagement, particularly when you hold numerous files to load prior to the content. Because JS and CSS files don’t denote any content to users, this conventional method to structure HTML may influence your user engagement data. You may alternatively put JS and CSS files at the bottom of your pages under the body tag.

It’s significant to allude to the fact that the web page still loads within the identical time period, yet its anticipated speed becomes drastically faster. Users discern content prior to JS and CSS files loading. Hence, it appears faster even though it loads within the same time period, an occurrence alluded to as actual speed opposed to perceived speed. An enlargement in perceived speed enhances user engagement unaccompanied by the necessity of increasing expensive server resources in your network.

4. Refrain From Using The ‘With’ Statement

While the ‘with’ statement may be handy for programmers, the processing speed is dreadful. Specifically, the ‘with’ statement represents shorthand code which permits the programmer to skip typing a variable name and solely reference properties and methods concerning the object deploying the dot (.) character. As this does make coding quicker and simpler, you must also keep in mind that the JavaScript engine loads every property and method rather than merely the ones referenced when the entire variable name is typed out.

Using ‘with’ is an extravagant way to code when speed is a concern and top priority. Therefore, it’s recommended to replace all ‘with’ references with variable names as you analyze your scripts.

5. Continually Deploy The ‘var’ Keyword For Variable Definitions

The ‘var’ keyword establishes a new variable, yet it isn’t a necessity. In circumstances where you don’t deploy ‘var’, the JavaScript engine is strained to search the whole scope chain. You will likely allot a variable with a returned function value, but don’t omit the ‘var’ declaration. This preserves processing time when the JavaScript engine can spot a local variable without needing to search the scope chain.

Besides deploying ‘var’, refrain from deploying global variables when a local one is adequate. Global variables in all languages are disliked since they always take considerable time to process and decreases the speed of the application.

6. Look Out For Your Loops, Particularly Nested Loops

Loops may be burdensome on any engine, though they are imperative. The ideal way to keep your code optimized is to ask whether a function can be utilized rather than deploying a complex loop. Commonly, functions that are greatly better for processing speed may replace those loops.

Nested loops may be particularly burdensome when you have numerous hundred records to iterate through. It’s also effortless to insert a bug in your code with excessive nested loops. Think about refactoring your code when you discover that loops are hindering your website.

7. Use Caching / CDN

Your JavaScript and CSS files seldom change. When you cache both, only the content on the web page has to be downloaded. If you happen to be using a CDN, then caching is already taken care of.

It’s a good idea to deploy a Content Delivery Network (CDN) nowadays as many are made available for free. Plenty well-known JavaScript libraries are accessible on CDNs. Two notable examples of libraries accessible on prevalent cloud hosts are JQuery and Bootstrap. Simply type in the CDN URL, and you don’t have to fret about retaining files kept on your server. CDNs will automatically cache objects which allows you to place emphasis on your local code rather than shared libraries.

8. Compressing Files Using GZip

GZip is a file compression program that decreases the size of your images and script downloads. You compress your files and save this version onto your server. The web browser will download the tinier, compressed version of the file and will extract it as the entire content transfers to the computer. Use GZip when your site retains numerous large files. It’s typical that image download sites deploy large files to display data. It may enhance your site’s load time which will also increase user engagement. Another advantage is that if you are paying a hosting provider that scales based on the resources you deploy, your costs could be diminished as well since you are saving storage space.


Optimizing JavaScript files is merely one solution for a slow site. If you have evaluated your site and found that it’s too slow, then an appropriate first measure is to assess JavaScript files and your code.

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