babel-to-go

Standalone build of babylon (babel's parser), babel-traverse, babel-types and babel-generate. It is intended to provide only enough functionality for a browser to round trip JavaScript source code to an AST and back, using babylon-traverse to examine and modify the tree. To reduce code size, much support for JSX, flow and other language features is removed. Additionally, source map support is removed from babel-generate.

This project is a fork of babel-standalone, though modified to serve a different purpose. Unlike babel-standalone, Babel-to-go does not search for and compile code found in the loading web page's DOM.

After gzip compression, babel-to-go.min.js is about 100KB in size. For comparison, babel.min.js is about 200KB after compression but has 100KB more features!

Example Usage

1<script src="babel-to-go.min.js"></script>
2<script>
3  var babylon = Babel.babylon;
4  var traverse = Babel.traverse;
5  var types = Babel.types;
6  var generate = Babel.generate;
7
8  var source = "for (var i = 0; i !== 3; ++i) {\n" +
9               "  console.log('Hello, World!');\n" +
10               "}\n";
11
12  var ast = babylon.parse(source);
13
14  traverse(ast, {
15    StringLiteral: {
16      exit(path) {
17        path.replaceWith(types.stringLiteral(
18          path.node.value.toUpperCase()));
19        path.skip();
20      }
21    }
22  });
23
24  var result = generate(ast);
25  var fn = new Function(result.code);
26  fn();
27
28  // Console output:
29  // HELLO, WORLD!
30  // HELLO, WORLD!
31  // HELLO, WORLD!
32</script>

Installing

Installing with npm is straightforward and probably what you want to do:

npm install babel-to-go --save

Alternatively, if building babel-to-go yourself, keep in mind that babylon is a submodule that needs to be initialized and updated. You could do something like this to build everything, passing --recursive to git clone to initialize and update submodules:

$ git clone --recursive https://github.com/alastairpatrick/babel-to-go.git babel-to-go
$ cd babel-to-go
$ npm install
$ npm run build
$ npm test

While dependencies like babel-traverse are simply listed in package.json, babylon is a submodule. The reason is because babylon is bundled as a single packed source file, which makes it difficult to subtract the unneeded plugin code, e.g. JSX and flow. By taking the babylon code directly from its git repository via a submodule, it is possible to extract the JavaScript parser minus its plugins.