Code for splitting Facebook's SDK into its constituent modules. Used for https://medium.com/@BenRegenspan/why-16-of-the-code-on-the-average-site-belongs-to-facebook-and-what-that-means-68956cd731be / https://docs.google.com/spreadsheets/d/1vdRzi-wlYNQOoAt4bGOseDMt7vgmpv9BoSfy4yM1SYY/edit#gid=873242422

Facebook SDK Splitting HOWTO

# Install NPM dependencies:
npm install babel-generator@6.26.0 babel-traverse@6.26.0 babylon@6.18.0

# Download Facebook's unminified SDK
wget https://connect.facebook.net/en_US/sdk/debug.js

# Run
node split-facebook-debug-js.js

split-facebook-debug-js.js

const babylon = require('babylon');
const traverse = require('babel-traverse').default;
const generate = require('babel-generator').default;
const path = require('path');
const amdPath = path.join(__dirname, 'amd');
const fs = require('fs');
const fb = babylon.parse(fs.readFileSync('debug.js').toString());

const modules = [];

// Traverse the AST and extract modularized code
traverse(fb, {
  enter (path) {
    if (path.isIdentifier({ name: '__d' })) {
      if (path.parent.type !== 'CallExpression') {
        return;
      }

      // Handle calls to __d() module definition function
      const { code, map } = generate(path.parent);
      modules.push({
        name: path.parent.arguments[0].value,
        code
      });

      // Remove the module from the AST
      path.parentPath.remove();
    }
  }
});

// Write out module files
modules.forEach((module) => {
  fs.writeFileSync(path.join(amdPath, `${module.name}.js`), module.code);
});

// Write out miscellaneous non-module code/module loader code
fs.writeFileSync(path.join(amdPath, `entry.js`), generate(fb).code);