Inject log code to JavaScript function

inject-logger.coffee

esprima    = require 'esprima'
escodegen  = require 'escodegen'
fs         = require 'fs'
estraverse = require('estraverse')

source = process.argv[2]

fs.readFile source, (err, origCode) ->
    logger = esprima.parse(
        'console.log("trace: " + arguments.callee.name, arguments);'
        ).body
    ast = esprima.parse(origCode.toString())
    estraverse.traverse ast,
        enter: (node, parent) ->
            if (node.type == 'FunctionExpression' || node.type == 'FunctionDeclaration')
                node.body.body = logger.concat(node.body.body)
        leave: (node, parent) ->
            if node.type == 'VariableDeclarator'
              console.log(node.id.name);
    newCode = escodegen.generate ast
    console.log(newCode)
    eval(newCode)