javascript - Is Babel a compiler or transpiler?

Question

I've been using Babel for a while now, and I've always been under the impression that Babel was a transpiler for converting my ES6 and ES7 JavaScript into ES5 JavaScript, as I was under the assumption that you could technically treat ES5 and ES6 as two different language.

However, I couldn't help but notice that Babel's website title describes it as a compiler, which I believe is something very different from a transpiler.

Is Babel a transpiler or a compiler, or perhaps offers both options? Or is the website's title simply incorrect?

Disclosure: I know this sounds like a very pedantic question, but I am writing documentation relating to Babel, and I want to ensure my description is accurate

Answer 1

The definitions of "transpiler" and "compiler" are blurry. Both of them do translate a program from one language to another language while keeping the behaviour.

We usually name it a "compiler" when it produces an executable binary. However, binary is just another language, which can be interpreted by a CPU. Every program is "executable" on the respective machine.

We usually name it a "compiler" when it produces a lower-level output than the input was, e.g. C to assembler. Or Java to Java bytecode. Or ES8 to ES5. Wait… is that really a different level?

We usually name it a "transpiler" when its output is on a similar level as the input, e.g. Python to JavaScript or the other way round. However, there always will be parts that use an abstraction available in one language that need to be "compiled" to a lower-level implementation in the other language.

So to answer your questions:

I believe a compiler is something very different from a transpiler.

No.

Is Babel a transpiler or a compiler, or perhaps offers both options?

Yes.

Or is the website's title 'Babel - The compiler for writing next generation JavaScript' simply incorrect?

No. That title focuses on next-generation features, i.e. higher-level abstractions that really need to be compiled into a very different output. Even though the output is still ordinary, mostly human-readable, JavaScript.

I am writing documentation relating to Babel, and I want to ensure my description is accurate

In that case, I'd use their own terminology from the official website. If you want to compare the tool to others, choose your own description.