Design and Build Your Own JavaScript Library: Tips & Tricks — SitePoint
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We always make use of libraries. Code that has been packed and ready for use in projects is called a library, and it helps developers save time and avoid having to start from scratch. Reusable packages, whether open-source or closed-source, are preferable to manually copying and pasting from previous projects or reconstructing the same feature.
But what exactly is a library, apart from packaged code? A library should always consist of one file, or multiple files within a single folder, with very few exceptions. When using its code in your project, it should be maintained independently and left exactly as is. Setting up configuration and/or behavior unique to a project should be possible with a library. Consider it a USB gadget that can only be reached via a USB port. Certain devices, including keyboards and mice, can be configured via an interface that comes with or is made by the device itself.
I shall describe the construction of libraries in this essay. This post is mostly concerned with creating a JavaScript library, even if the majority of the concepts discussed are applicable to other languages.
Libraries, first and foremost, greatly facilitate the reuse of preexisting code. All you need to do is pull in the library instead of having to find an old project and copy some files. Additionally, by fragmenting your application, you may keep its codebase smaller and manage it more easily.
Any code that simplifies the process of doing a certain task and is reusable, such as an abstraction, is a good candidate to be included in a library. One intriguing instance is jQuery. Even while the jQuery API is much more than just a streamlined DOM API, it was quite helpful a few years back when cross-browser DOM manipulation was still somewhat challenging.
People are more likely to join in and contribute to an open-source project by reporting bugs or adding to the code base if it gains popularity and is used by more developers. In either case, the library and all the projects that rely on it will gain from it.
Excellent prospects can also arise from a well-liked open-source project. Your efforts may impress a corporation, which may extend an employment offer to you. Perhaps you'll be asked to assist in integrating your idea into an application by a corporation. Nobody knows your library like you do, after all.
For many, it's just a hobby—they like writing code, lending a hand to others, and developing themselves in the process. You can experiment and push your boundaries.
Your library should have a clear purpose before you write the first line of code. You must set goals. You can stay focused on the issue you want to use your library to address with them. Remember that your library should be simpler to use and recall than the original problem. Users will find it easier to learn how to utilize your library the simpler the API is. To paraphrase the Unix ideology:
Regardless of the library's size, attempt to create a roadmap. Make a list of every feature you desire, then eliminate as many as you can until you have a small but useful library—a minimal viable product, if you will. It's going to be your debut release. Every new feature can then have milestones created for it. By effectively segmenting your project into manageable pieces, you're increasing the sense of accomplishment and enjoyment from each feature. This will keep you sane, I promise.
I personally find it quite helpful to approach my library from the viewpoint of the user. It could be referred to as user-centric design. You are essentially sketching out your library, presumably with more consideration and to make it more user-friendly for those who decide to utilize it. Simultaneously, you might consider whether features ought to be adjustable—a topic covered in a later section of this piece.
Using your library in your own projects and eating your own dog chow is the ultimate measure of an API's quality. Try using your library in place of application code to determine if it has all the capabilities you need. Aim to keep the library as simple as possible, but allow for enough customisation (discussed later in this article) to make it functional for their edge cases as well.
The structuring of your library may also require considerable consideration, depending on its complexity. Design patterns are an excellent approach to organize your library and even solve some technological issues. When adding new features, it also lessens the chance of having to refactor significant portions.
Libraries are fantastic because of their flexibility, but it can be hard to tell what can be customized and what can't. Chart.js vs. D3.js is a prime illustration of that. These are both top-notch libraries for data visualization. The creation and styling of several built-in chart kinds is quite simple with Chart.js. But D3.js is what you need if you want more graphic customization.
The user can be granted control in a number of ways, including through callbacks, events, and configuration that exposes public methods.
While most libraries allow you to change settings at run-time, other libraries only allow you to do so during initialization. Changing these options shouldn't accomplish anything more than updating their values for later usage because they are frequently restricted to small bits and portions.
It is possible to expose methods to work with an instance; for example, getters and setters can be used to put and retrieve data from and perform operations on the instance, respectively.
Public methods can occasionally pass callbacks, which are typically used to execute user code following an asynchronous task.
Events are full with possibilities. Callbacks and them are comparable, but adding event handlers shouldn't cause actions to happen. You guessed it: events are frequently used to indicate other occurrences! You can include further details and return a value for the library to use, much like in a callback.
Sometimes it's a good idea to let users add more resources to your library. You have two options for this: either do nothing and let users access your library's namespace, or provide a public function or field that they can populate, similar to Angular modules (angular.module('myModule')) and jQuery's fn (jQuery.fn.myPlugin):
In a similar vein, this also lets you overwrite methods.
If the latter, you will have less control over how extensions and plugins are defined because users will be able to access your library's namespace. You can—and should—write documentation to ensure that extensions adhere to certain conventions.
Test-driven development is best started with the creation of an overview. To put it briefly, this is the process of outlining requirements in the form of tests before creating the library itself. Behavior-driven development is the approach used if these tests determine whether a feature behaves as it should and you write those before developing your library. In either case, you can fairly assume that your library functions if all of its features are covered by your tests and all of your code passes them.
Unit Test Your JavaScript Using Mocha and Chai by Jani Hartikainen contains instructions on writing unit tests with Mocha. Tim Evko demonstrates how to create a lovely testing pipeline using the Jasmine framework in Testing JavaScript with Jasmine, Travis, and Karma. There exist numerous testing frameworks in various variants, but these two are highly favored.
Comments on the expected output were already included in my plan that I made earlier in this essay. All tests begin here, with an expectation. This is how a Jasmine test for my library might appear:
It's time to start considering architecture and the intended use of your library once you're fully satisfied with the API design for your initial release.
A module loader may or may not be used. You should make your library compatible with module loaders, though, since the developer who decides to implement your library might choose to do so. Which one, though? How do you decide between AMD, RequireJS, CommonJS, and other options?
You don't actually have to! Several module loaders can be supported through the use of Universal Module Definition (UMD). Snippets come in a variety of flavors, but to make your library UMD-compatible, you can also find versions on the UMD GitHub site. Module loaders are not an issue if you use one of the templates to get your library started or if you use your preferred build tool to add UMD.
If you want to use the import/export syntax for ES2015, I strongly advise use Babel for ES5 compilation together with Babels UMD plugin. This will enable you to create a library that is suitable for everyone while utilizing ES2015 in your project.
I support comprehensive documentation for any project, but it's sometimes put off and subsequently forgotten because it seems like a lot of work.
Basic details like the project name and description should always be included at the beginning of documentation. It will make it easier for others to comprehend what your library does and if it's a good fit for them.
To help educate users, you may include details like the scope and goals as well as a roadmap that will let them know what to expect going forward and how they can get involved.
It goes without saying that you must instruct people on how to utilize your library. The documentation for the API comes first. Although they are excellent features, authoring tutorials and examples may be somewhat labor-intensive. But inline documentation isn't. With JSDoc, these comments may be processed and transformed into documentation pages.
It's possible that some people may like to alter your library. Most of the time, this will be for contribution, but some people could wish to make a unique build for themselves. Documentation for meta-tasks, such as a list of commands to build the library, run tests, produce, convert, or download data, is helpful for these users.
Contributions are fantastic when your library is open-sourced. You might include documentation to help contributors by outlining the requirements and the actions involved in making a contribution. It will facilitate both their correct execution and your ability to evaluate and accept their contributions.
Don't forget to include a license. In theory, it will still remain copyrighted if you decide not to include one, although not everyone is aware of that.
ChooseALicense.com is a fantastic tool for selecting a license without having to be an expert in law, in my opinion. Simply store the text in a LICENSE.txt file located in the root of your project after selecting a license.
A strong library must have versioning. A user is likely to want to stick with the version that works for them if you ever decide to make breaking changes.
Semantic Versioning, or SemVer, is the de-facto standard for version naming as of right now. SemVer versions are denoted by three numbers: major, minor, and patch, each of which represents a distinct modification.
You can add version numbers to your git repository if you have one. You may think of them as snippets from your repository. We refer to them as tags. Open the terminal, type the following to create a tag:
A lot of platforms, such as GitHub, will include all of your versions along with download links.
A package manager is either included with many computer languages or can be obtained from a third party. We can import libraries designed especially for those languages thanks to them. RubyGems for Ruby and PHP's Composer are two examples.
Npm is included with Node.js, which is a kind of standalone JavaScript engine. If npm is unfamiliar to you, our beginners guide is a wonderful place to start.
Your npm package will be made publicly available by default. Do not be alarmed! In addition, you can create a secret registry, publish private packages, or not publish anything at all.
Your project needs a package.json file in order to publish your package. Alternatively, you may utilize the interactive wizard to do it manually. Enter to launch the wizard:
Your git tag and the version property should match. Make sure you have a README.md file as well. Npm uses that for the package presentation page, just like GitHub does.
That's it! Your npm package is now public.
Another package manager named Bower appeared a few years ago. However, this package manager is made for a certain platform—the web—rather than a particular language. All of the main front-end assets are located right there. It is only worthwhile to publish your package on Bower if your library is browser-compatible.
We also have an introduction to Bower guide available if you're not familiar with it.
You can also set up a private repository, much like with npm. Additionally, you have the option to stop the wizard from publishing it entirely.
Remarkably, a lot of people seem to be switching to npm for front-end assets during the last year or two. Many front-end packages are also published on npm, even though the majority of npm packages are written in JavaScript. In any case, Bower is still widely used, so you should publish your package there as well.
Did I mention that Bower was originally inspired by and is in fact a npm module? The instructions are remarkably similar. Type this to create a bower.json file:
The instructions are self-explanatory, much like npm init. Lastly, to make your package public:
The library is the main offering. Make sure it is stable, easy to use, and solves an issue, and you will delight your team and several engineers.
Many of the things I listed can be done automatically, including running tests, making tags, updating package.json with the new version, and republishing your package to bower and npm. This is the point at which you employ Travis CI or Jenkins, or other continuous integration systems. This is covered in part in the Tim Evko piece I previously cited.
Building your own JavaScript library offers a number of advantages. First of all, it lets you reuse code for other projects, which will ultimately save you time and effort. It also facilitates a more orderly and readable organization of your code. When cooperating with other developers or working on bigger projects, this is especially helpful. Finally, building your own library can help you gain a deeper understanding of software development principles and JavaScript. It can be a terrific learning experience.
Determining the goal of a JavaScript library is the first stage in the creation process. What features would you like to see in your library? You may begin creating the code for your library once you have a clear notion of what you want it to do. Usually, this entails defining a number of functions that together offer the required functionality. Other developers can then access and utilize these functions via a public API.
An essential component of creating a JavaScript library is testing. For JavaScript, there are numerous testing frameworks available, including Jest, Mocha, and Jasmine. With the help of these frameworks, you can create unit tests to make sure your functions operate as intended. You might want to develop integration tests in addition to unit tests to make sure all the components of your library function as intended.
Any software library must have excellent documentation. It makes it easier for other developers to comprehend the functions in your library and how to use them. Every function in your library needs to have a thorough description that covers all of its inputs, outputs, and potential side effects. Additionally, you may utilize programs like JSDoc to have documentation created from your code comments automatically.
A JavaScript library can be distributed in a number of ways. A typical approach is to post it on a package manager such as npm. This enables other developers to quickly and simply use a single command to install your library. Moreover, you can offer a download link on your website or put your library on a content delivery network (CDN).
Fixing problems, incorporating new features, and keeping the library current with the most recent JavaScript standards and practices are all part of maintaining a JavaScript library. It's critical to frequently test your library and pay attention to user comments. Versioning your library is something else you should think about, so users have the option to utilize the most recent version with new features or the stable version.
You should concentrate on developing clear, succinct code if you want your JavaScript library to be effective. Steer clear of pointless calculations and memory usage. Utilize resources such as Chrome DevTools to profile your library and locate any areas where performance is hindered. Minifying your library is another option to think about if you want to minimize file sizes and speed up load times.
Because every browser interprets JavaScript differently, ensuring browser compatibility can be difficult. To transpile your code into a JavaScript version that works with older browsers, utilize tools such as Babel. To find and address any compatibility problems, you should also test your library across a variety of browsers.
An essential component of creating a JavaScript library is error handling. Your goal should be to offer users with error messages that are easy to comprehend and indicate what went wrong. Try/catch blocks are a useful tool for handling and catching mistakes. Additionally, you want to think about giving users a mechanism to report problems and defects.
You can solicit comments on your JavaScript library in a number of ways. You can publish your library on a package manager like npm, publicize it on forums or social media, or ask other developers to review your work and provide feedback. It's important to be receptive to criticism and flexible enough to adjust your approach in response to input.
Tim Severien is a Dutch front-end developer who is excited about Sass and JavaScript. He writes articles for SitePoint or Tim's blog when he's not writing code.
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