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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

<script src="babel-to-go.min.js"></script>
<script>
  var babylon = Babel.babylon;
  var traverse = Babel.traverse;
  var types = Babel.types;
  var generate = Babel.generate;
 
  var source = "for (var i = 0; i !== 3; ++i) {\n" +
               "  console.log('Hello, World!');\n" +
               "}\n";
 
  var ast = babylon.parse(source);
 
  traverse(ast, {
    StringLiteral: {
      exit(path) {
        path.replaceWith(types.stringLiteral(
          path.node.value.toUpperCase()));
        path.skip();
      }
    }
  });
 
  var result = generate(ast);
  var fn = new Function(result.code);
  fn();
 
  // Console output:
  // HELLO, WORLD!
  // HELLO, WORLD!
  // HELLO, WORLD!
</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.