Transpiling

Transpiling refers to the process of converting code written in one version of the language (typically a newer version with advanced features) into an equivalent code in an older version that is more widely supported by browsers and environments. This is primarily done to ensure compatibility with older browsers that may not support the latest JavaScript features.

The term “transpiling” is a combination of “transform” and “compile,” emphasizing that the process involves transforming source code from one form to another while still maintaining its high-level nature.

How Transpiling Works

1. Source Code: You write your code using the latest features and syntax, often from newer versions of JavaScript (e.g., ES6+).
2. Transpiler: A transpiler, such as Babel, takes your modern JavaScript code and converts it into an older version of JavaScript that can be executed in most web browsers and environments.
3. Compatibility: The transpiled code now works across a broader range of browsers, including older ones that lack support for newer language features.

Transpilers are particularly useful for developers who want to use the latest JavaScript features without sacrificing compatibility.
This is crucial in web development, where different browsers have varying levels of support for new language features.
By using a transpiler, developers can leverage modern language constructs and syntax while ensuring their code runs smoothly on a wide array of browsers.

It’s important to note that while transpilers can provide backward compatibility, they can’t enable features that fundamentally rely on new browser APIs or behaviors. In those cases, polyfills or alternative approaches might be necessary.

Transpiling Example: Default Parameter Values

ES6 introduces default parameter values in functions. Here’s a simple example:

ES6 Syntax

function foo(a = 7) {
  console.log(a);
}
foo();      // 7
foo(25);    // 25
  

While this ES6 syntax is straightforward and helpful, it’s not supported in older browsers. So, how does a transpiler handle it to work in older environments?

Transpiled Code

function foo() {
  var a = arguments[0] !== undefined ? arguments[0] : 7;
  console.log(a);
}
  

The transpiled code checks if arguments[0] is undefined and assigns the default value of 7. Otherwise, it uses the passed value. This transpilation not only enables the use of modern syntax in older browsers but also clarifies the intended behavior.

The transpiled version makes it clearer that undefined is the only value that can’t be explicitly passed as a default parameter, which may not be immediately evident from the ES6 code.

In summary, Using a transpiler as a standard practice allows you to adopt newer syntax when it becomes valuable, instead of waiting for older browsers to catch up over time. Transpilers are instrumental tools that developers commonly integrate into their development workflows and command-line environments. Their usage varies based on specific code and project requirements. It’s essential to recognize that transpilers are not built from scratch for each project; instead, they are existing tools that facilitate code transformation. Here are some notable choices:

• Babel (formerly 6to5): This transpiler expertly converts ES6+ code into ES5, making it widely compatible.
• Traceur: With its capabilities to transpile ES6, ES7, and even future versions into ES5, Traceur stands as a versatile choice.