debug with vscode --document is not defined

i debug the code with vscode ,follow the Course（https://medium.com/@drcallaway/debugging-es6-in-visual-studio-code-4444db797954），but Report errors

var doc = document, win = window, ArrayProto = Array.prototype, slice = ArrayProto.slice, filter = ArrayProto.filter, push = ArrayProto.push; ^ ReferenceError: document is not defined at /Users/smartcoach/grapesjs/node_modules/cash-dom/dist/cash.js:13:13 at doc (/Users/smartcoach/grapesjs/node_modules/cash-dom/dist/cash.js:8:22) at Object.<anonymous> (/Users/smartcoach/grapesjs/node_modules/cash-dom/dist/cash.js:12:3) at Module._compile (module.js:649:30) at Object.Module._extensions..js (module.js:660:10) at Module.load (module.js:561:32) at tryModuleLoad (module.js:501:12) at Function.Module._load (module.js:493:3) at Module.require (module.js:593:17) at require (internal/module.js:11:18) Waiting for the debugger to disconnect...

I want to learn by debug ，please help.