On windows, after 'npm install' has completed, the very last postinstall command for protractor fails on windows. It looks like the other commands are prefixed with 'node' but this one is not which results in the following error:
'.' is not recognized as an internal or external command, operable program or batch file.
The command:
./node_modules/protractor/bin/webdriver-manager update
A quick workaround is to simply run the same command but prefixed with 'node' which worked. e.g:
node ./node_modules/protractor/bin/webdriver-manager update