You'll want to supply server-static with an absolute path to angularjs to ensure it's searching in the expected path.
You can use the script's __dirname as the base for it:
...serveStatic(__dirname + '/angularjs')...
Or with path.join():
var path = require('path');
// ...
...serverStatic(path.join(__dirname, 'angularjs'))...
This is because the file system module, that serve-static is using, resolves relative paths from the current working directory (process.cwd()).
So, whether ../angularjs resolves to /path/to/node/angularjs depends on which directory server.js is started from.
Currently, it could work from /path/to/node/angularjs/:
$ cd /path/to/node/angularjs
$ node ../server.js
# resolves: '/path/to/node/angularjs' + '../angularjs'
# to: '/path/to/node/angularjs'
Or, by changing the ../ (parent directory) to ./ (current directory), it could be started from /path/to/node instead:
...serveStatic('./angularjs')...
$ cd /path/to/node
$ node server.js
# resolves: '/path/to/node' + './angularjs'
# to: '/path/to/node/angularjs'