Crafting Browser-Compatible JavaScript Code with BabelJS

The Rise of JavaScript Compatibility Issues

Not so long ago, the compatibility problems due to old browsers made it quite hard for the developers to solve. After the open source communities showered comprehensive support for the JavaScript frameworks/libraries, JS became viral in web development world. In the beginning however, hardcore developers had concerns. It seemed that the JavaScript was as powerful as it was heavy on the efficiency. But with rapid development in browser and digital technology, it was possible for the JS community to flourish.

With more and more developers contributing to the community, more and more framework versions came into existence. On the other hand, all browsers evolved with different philosophies following what they thought was the idea of perfection. Not all JavaScript innovations were picked up by the list of browsers for native support. This in-turn resulted in a huge gap between JavaScript language and it’s blanket support by all browsers. The older versions however were left in shambles, they lacked the support for the JavaScript. Even the different versions of frameworks when put together added to the developer’s anxiety.

Key Takeaway: JavaScript compatibility gaps appear because browser engines adopted new language features at different speeds, which leaves older browser versions unable to run current syntax.

Leveraging Babel for Browser Compatibility

Babel is a transpiler and a brilliant one indeed. Everyday developers face challenges when integrating the functionalities of different libraries. Different versions of JavaScript often lead to messy botched up jobs, reason for compromised efficiency. Transpilers are often mistaken for compilers, but they are a bit different. They work on the source code and return a more sturdy compatible source code only. Developers can even customize Babel to suit them better.

Key Takeaway: A transpiler such as Babel returns source code in the same language, unlike a compiler that produces a different and lower-level target.

How does it work?

Babel’s function is pretty straightforward and easy. It converts incompatible source code or the library functionality into browser supported code which your browser may find compatible. Babel does that in 3 simple steps.

Parsing

The first thing it does is finding the unsupported or incompatible parts in the code that is passed. It does that by using AST (Abstract Syntax Tree).

Transforming

The highlighted part of the source code is transformed into the compatible one. This is done with the help of the AST so as not to handicap any functionality of the program. You can even customize your own Babel plug-in.

Generation

You have now the transformed code, now you need additional plugins that will help you effectively use the transpiled code. Source map helps you in this, it works well with the V8 (chrome & node js). It allows you take the transpiled to the address website url for it to parse.

Key Takeaway: Babel runs three stages in order, parsing source into an Abstract Syntax Tree, transforming the unsupported nodes in that tree, then generating browser-compatible output code.

Additional Babel Plugins used for Compatibility

Babel alone is not enough for your JavaScript to be compatible. You need more tool so for efficient cross browser compatibility. Webpack is another tool that helps in reducing the bundle size. Sourcemap mentioned earlier is also useful when bundling or catenating. Babel too has a lot of Presets that are used to transpile the new JavaScript code for the old browsers or solving the ECMAScript version problems. Polyfill in Babel includes a custom regenerator runtime and core.js. It emulates ES2015+ custom environment which is used in applications, meaning you can even use new built-ins like Promise, weakmap along with a couple of new Array functionalities. It automatically loads with babel.

Leading JavaScript framework/libraries like React too have abundant use of this amazing tool.

Key Takeaway: Babel rewrites syntax only, so bundlers such as Webpack and polyfills from core-js are still required before a modern JavaScript build runs on an older browser.

Is Babel Still Needed For Modern Browsers?

Yes, but Babel does far less work than it once did. Every major browser engine runs ES2015+ natively, so @babel/preset-env emits only the transforms your declared targets actually require.

Four changes affect how you configure Babel:

• Internet Explorer 11: Microsoft retired the Internet Explorer 11 desktop app on 15 June 2022, so the default browserslist query no longer targets it and preset-env skips the heaviest transforms.
• @babel/polyfill: Babel deprecated the @babel/polyfill package at version 7.4.0. Import core-js/stable and regenerator-runtime/runtime directly, or set useBuiltIns with a corejs version in preset-env.
• browserslist targets: preset-env reads .browserslistrc or the browserslist key in package.json, so one target list drives Babel and Autoprefixer together instead of two separate configs.
• esbuild and SWC: Next.js switched its default compiler to SWC, and esbuild downlevels syntax in Go. Babel stays the right choice when you need custom plugins, macros, or an unusual transform.

Confirm the output where you promised it runs. A build that targets older browsers is only proven by cross browser testing on those engines, and feature-level checks such as javascript promises browser support show what the polyfill layer still has to cover.

Key Takeaway: Babel is still needed for modern browsers, but its job has narrowed to the transforms a project's browserslist targets demand plus any custom plugin work.

Conclusion

It is genuinely a great tool that has potential to resolve a lot of cross browser compatibility issues in JavaScript code. We wanted to give back to the community for showering so much love on us. TestMu AI is proud to announce that we support Babel and want it to be a great success. Till then, Keep Testing!