Error code: 800A1391 Source: Microsoft JScript runtime error Running Grunt - Module is undefined

New Grunt user here who is using a lot of new tools (npm nodejs) today.

I've got Grunt "installed" and have been able to create a grunt.js file using the init task as described here: http://net.tutsplus.com/tutorials/javascript-ajax/meeting-grunt-the-build-tool-for-javascript/ and here: https://github.com/cowboy/grunt/blob/master/docs/getting_started.md. But whenever I run the "grunt" command I get an error:

Windows Script Host
Script: c:\users\[]\Documents\code\grunt\grunt.js
Line: 2
Char: 1
Error: 'module' is undefined
Code: 800A1391
Source: Microsoft JScript runtime error

As explained in the FAQ, you need to type grunt.cmd instead on Windows because the OS tries to launch grunt.js

Or you can install grunt-cli globally instead. This package will run any version of Grunt if it's been installed locally to your project.

If you're getting a "Microsoft JScript runtime error" that means that node.js isn't even getting invoked; instead Windows Script Host is trying to run your code. That's probably a problem with filetype associations; IIRC Windows defaults to trying to execute a ".js" file with WSH. You may wind up having to create a shortcut to your script, specifying a command line (probably something like "node %1") and a starting directory in order to make sure that it's executed properly.

It would help if you could tell us exactly how you're trying to invoke your code.

it seems that in the latest versions of the grunt modules, you would have to do the following to have it work under windows:

remove any globally installed grunt

npm uninstall -g grunt

install grunt-cli globally

npm install -g grunt-cli

install grunt locally into your project

npm install grunt

installing grunt (v0.4.x) globally does not seem to create the necessary grunt.cmd anymore. it seems that the recommendation is now to have grunt installed locally to be able to use version-specific Gruntfiles

As Florian F suggested, running grunt.cmd works. This is because of the process Windows is looking for your grunt command.

When typing grunt -h Windows will proceed to look for the following files:

  1. ./grunt.cmd
  2. ./grunt.* (grunt.js is found in this case which is why you see "module is undefined")
  3. %APPDATA%/npm/grunt.cmd

An alternative to using "grunt.cmd" is to use grunter which simply renames the command to grunter... then you no longer have this problem.