eval module with local variables

eval.js

const CLIEngine = require("eslint").CLIEngine;

function getIdentifiers(code) {
  if (!code) {
    return [];
  }

  var cli = new CLIEngine({
    envs: ['browser', 'node'],
    useEslintrc: false,
    parserOptions: {
      "ecmaVersion": 2016
    },
    rules: {
      'no-undef': 1
    }
  });
  var report = cli.executeOnText(code);

  return report.results[0].messages.map(msg => msg.message.match(/'(.+?)'/)[1])
}

const targetCode = `
const localVar = 'local value';

const sameNameVar = 'inner new value';

console.log('local var:', localVar);

console.log('same name var:', sameNameVar)

console.log('var from context:', contextVar);

try {
  console.log('var not existed', notExisted); // this will cause exception
} catch(ex) {
  console.log('should catch exception here:', ex.message)
}
`

function copyLocalVarToContext(vars) {
  const codes = [];
  for (let i = 0; i < vars.length; ++i) {
    const id = vars[i];
    codes.push(`if (typeof ${id} !== 'undefined') context['${id}'] = ${id};`)
  }
  return codes.join('\n');
}

function extract(context, contextName) {
  const codes = [];
  Object.keys(context).forEach(id => {
    codes.push(`const ${id} = ${contextName}['${id}'];`)
  })
  return codes.join('\n');
}

function main() {
  const ids = getIdentifiers(targetCode);

  const contextVar = 'outer value';
  const sameNameVar = 'outer old value';

  const context = {};
  eval(copyLocalVarToContext(ids));

  const contextName = `__context_${(new Date()).getTime()}_${Math.random().toString().replace(/\./g, '')}__`

  const fnCode = [
    extract(context, contextName),
    '//////',
    targetCode
  ].join('\n')

  const fn = new Function(contextName, fnCode)
  // console.log(fn.toString())
  // console.log(context)

  fn(context)
}

main()