babel-core/lib/babel/build-helpers.js

Turn ES6 code into readable vanilla ES5 with source maps

var File = require("./transformation/file");
var util = require("./util");
var each = require("lodash/collection/each");
var t    = require("./types");

module.exports = function (body, namespace) {
  each(File.helpers, function (name) {
    var key = t.identifier(t.toIdentifier(name));
    body.push(t.expressionStatement(
      t.assignmentExpression("=", t.memberExpression(namespace, key), util.template(name))
    ));
  });
};