JSLint is readily available at the command line, and is very easy to plug in to your text editor's build system.
There is also the somewhat friendlier JSHint as a reasonable alternative: http://www.jshint.com/
There is also the somewhat friendlier JSHint as a reasonable alternative: http://www.jshint.com/
A not insignificant portion of the people taking those courses will not be command line savvy.
Also, I think that the fascination some programmers have for tools that are cumbersome and difficult to use is unhealthy.
The tool should not itself be the problem.
The tool should be a force multiplier that lets you solve other problems more easily.
By "Command line", the OP meant that it's easy to plugged it wherever you want it; i.e. it is not strictly an online tool.
About:
"fascination some programmers have for tools that are cumbersome and difficult to use is unhealthy"
Is 'grep' hard to use? What about ctrl+shift+f in Visual Studio? Which one is the most cumbersome and difficult to use? Highly subjective imo.