Every now and again we have to deal with legacy code, wading through dark and eerie sides of the code base, often with a vague, ambiguous and unsettling documentation — if any is provided at all. In such cases, refactoring the component seems inevitable.

Or perhaps you need to manage dates and arrays, or manipulate DOM — there is just no need to add an external dependency for a simple task of that kind, but we need to figure out the best way to do that. It’s always a good idea to explore lightweight vanilla JavaScript snippets as well — preferably the ones that don’t have any third-party dependencies. Fortunately, there is no shortage in tooling to do just that.

30 Seconds Of Code

30 Seconds of Code features a huge repository of short code snippets for JavaScript, including helpers for dealing with primitives, arrays and objects, as well as algorithms, DOM manipulation functions and Node.js utilities. You can also find plenty of small utilities for Python, React Hooks, React Components and Node.js. It also features useful JavaScript cheatsheets.

HTML Dom

HTML Dom provides over 120 bulletproof, plain JavaScript snippets for everything from toggling password visibility to creating resizable split views — all supported for modern browsers and IE11+.

Vanilla JavaScript Toolkit

Vanilla JavaScript Toolkit provides a growing collection of vanilla JavaScript methods, helper functions, plugins, boilerplates, polyfills, and learning resources. Also, Chris Ferdinandi runs a Vanilla JS Academy, with plenty of daily developer tips on Vanilla JS sent in his newsletter.

Micro-Libraries Under 5K

Micro.js is a curated repository of small JavaScript libraries and utilities, collected by Thomas Fuchs. All libraries are grouped, and are below 5k in size, doing one thing and one thing only — and doin it well.

Single Line Of Code

Phuoc Nguyen has released Single-Line-Of-Code, a repository of JavaScript utilities for everything around arrays, date and time, DOM manipulations, functions, numbers and objects.

Vanilla JS Code Challenge

30 Days Vanilla JS Code Challenge is a free video course by Wes Bos where you’ll learn to build 30 things in 30 days, with 30 tutorials — without any frameworks, compilers, libraries or boilerplates. That’s a great way to boost your JavaScript skills. You can also get all 30 days challenges and solutions as a GitHub repo.

Vanilla JavaScript video crash course is another free video course with 43 sessions, starting out with JavaScript DOM all the way to async JS, Babel and Webpack and a JavaScript password generator.

Migrating from jQuery to Vanilla JavaScript

If you still find yourself in the land of legacy systems running on jQuery, there is a number of resources that allow you to slowly move away from jQuery with more lightweight and standardized options:

• PlainJS, You Might Not Need jQuery and You Don’t Need jQuery are great references for vanilla JavaScript snippets. The sites feature repositories of code snippets for everything from UI and inputs to media, navigation and visual effects (with use cases not just for jQuery, but pretty much any legacy code).
• Learn Vanilla JS features books, courses, evergreen resources, communities, podcasts all around vanilla JS. A fantastic repository that’s worth keeping close.
• JavaScript Framework Diet is Sebastian De Deyne’s ongoing series on common tasks, solved without JavaScript frameworks. You’ll learn about selecting element, event delegation, file structure, dropdowns and enter and leave transitions.

Natively Format JavaScript Dates And Times

Do we still need libraries like Moment.js or date-fns to format JavaScript dates and times? With native browser capabilities being quite good these days and browser support being great, too, not necessarily, as Elijah Manor points out.

Elijah summarized three different methods for dealing with time and dates. The toLocaleDateString method comes in handy when you want a date that contains only numbers, a long wordy date, or one that outputs in a different language. If you only need to output the time portion of a JavaScript date object, there’s toLocaleTimeString.

Finally, the generic method toLocaleString lets you pass one or all of the options from the former ones into one method. Elijah built a CodeSandbox playground where you can experiment with the different approaches.

this vs. that

The deep knowledge of a subject really lies in understanding subtle differences between alternate ways of solving the same problem. How is nodeName different from tagName? How are the two increment operators different, e.g. ++value and value++? this vs. that is a friendly reference site for sorting out just this kind of questions.

The growing little repository by Phuoc Nguyen explains differences between properties and functions for JavaScript and TypeScript, as well as DOM, HTML and CSS. Also, WTF.js is a growing repository of common headaches, gotchas and unexpected behaviors around JavaScript.

Writing Clean, Reusable Code

No one likes to deal with badly written code, but in reality it happens all too often. To help us do better, Ryan McDermott adapted the software engineering principles from Robert C. Martin’s book Clean Code for JavaScript. The result is a practical guide to producing readable, reusable, and refactorable software in JavaScript.

From making variables meaningful and explanatory to limiting the amount of functions and dealing with error handling, the guide compares good and bad code examples. Of course, not every principle has to be strictly followed, but the guidelines help you assess the quality of the JavaScript code you and your team produce.

JavaScript The Right Way

Learning a new language can be quite a challenge, especially when there are so many tools and frameworks out there to get the most out of it as there are in the case of JavaScript. To prevent you from getting lost in all the possibilities and help you learn the best practices from the ground up instead, William Oliveira and Allan Esquina put together the guide “JavaScript The Right Way”.

Aimed at both beginners and experienced developers who want to dive deeper into JavaScript best practices, the guide gathers articles, tips, and tricks from top developers, covering everything from the very basics to code style, tools, frameworks, game engines, reading resources, screencasts, and much more to make a developer’s life easier. The guide is available in eight languages. A gold mine full of JavaScript wisdom.

And if you need another deep dive into JavaScript, Kyle Simpson's You Don't Know JS is always a good starting point (Kyle is working on the second edition at the moment, and also has plenty of books and video courses to explore).

Picking The Right JavaScript Framework

There are plenty of options when choosing a new JavaScript framework. But do you need one? And if so, how do you pick the right one? Sacha Greif’s 12-Points-Checklist highlights 12 things to keep in mind when evaluating any new JavaScript library. Most notably, features, performance, learning curve, compatibility and track record.

Perf-Track tracks framework performance at scale. It basically tracks the performance in terms of Core Web Vitals for Angular, React, Vue, Polymer, Preact, Ember, Svelte and AMP — on mobile and on desktop. The data set is currently still from 2020, but it gives us some insights into how well sites with these frameworks perform in the wild. For example, React with Gatsby perform better than the ones created with Create React app.

Tim Kadlec also conducted some research around that, comparing jQuery, Vue.js, Angular and React. The end result: the current crop of frameworks isn’t doing enough to prioritize less powerful devices and help to close the gap between desktop and mobile. These figures might give you at least some context to make a more informed decision.

Standalone Vanilla JS Libraries

The libraries below are tiny, vanilla JavaScript libraries without any dependencies. Just as they are lightweight, sometimes you might need to make some adjustments, e.g. to provide announcements to screen readers, or support legacy browsers. You might want to check a Complete Guide To Accessible Front-End Components as well.

• 360-degree view
  ThreeSixty.js is a tool for turning an image sprite into 360 degree image.
• Animation
  Anime.js is a lightweight animation library that works with CSS properties, SVG, Dom attributes and JavaScript objects. Also, Sal.js is a lightweight scroll animation library.
• Data Visualization
  Clusterize.js is a small JavaScript library for displaying large data sets.
• Filtering
  MixItUp 3 provides animated filtering, sorting, insertion and removal.
• Forms
  Choices.js is a configurable <select>-box/text input plugin.
• Image full screen preview
  Intense Image Viewer, a library for viewing images in full screen.
• Image gallery
  PhotoSwipe, supports touch gestures and Browser History API.
• Masonry Layout
  Columns.js and Waterfall.js are options for Masonry layout written in Vanilla JavaScript.
• Media Player
  Media Player, a cross browser, accessible, customizable media player written in plain JavaScript.
• Modals
  accessible_modal_window by Scott O’Hara.
• Parallax
  Rellax.js is a lightweight vanilla JavaScript parallax library (if you absolutely need one).
• Reactive states
  Reef, a lightweight library for creating reactive, state-based UI.
• Search
  InstantSearch.js is an an open-source UI library that lets you build a search interface in your front-end application.
• Sliders and carousels
  Siema, Glide, Splide.js and Swipe.js.
• Slideout navigation
  Slideout.js is a touch slideout navigation menu for mobile views.
• Spinners
  Spin.js dynamically creates spinning activity indicators, no images or dependencies needed, distributed as a native ES module.
• Sticky elements
  HC-Sticky makes any element on the page visible while a custom is scrolling. (Also consider using position="sticky" in CSS instead).
• Sticky navigation
  MenuSpy, a small JavaScript for sticky navigation bars that change as a user scrolls pas the parts of the page.
• Table filters and lists
  List.js adds search, sort and filters to plain HTML lists and tables.
• Table sorting
  Tablesort is a simple sorting component for tables.
• Transitions
  Barba.js is a great alternative to parallax, with fluid and smooth transitions between pages.
• Tilting
  Tilt-Vanilla.js is a smooth 3D tilt JavaScript library.
• Typewriter Text Effect
  Typewriter JS generates a typewriter effect.
• Visual sparkles
  Speckle.js is a JavaScript module that adds responsive, stylized speckles to any element.
• WYSIWIG Text Editors
  Froala, Etherpad and SunEditor are vanilla JavaScript WYSIWIG text editors. And if you want to build your own, ContentTools is a library for building WYSIWIG editors for HTML content.