To be honest I’m not sure why, but there seems to be some errors using node.js v5 and ionic at the moment. I’ve had similar issues, but reverting back to Node.js 4.2.2 fixed the problems.
yep nodejs 5 doesnt work for me… so use 4.2.2 if you have node as a dependencies for other big frameworks like cordova, ionic etc. you should use the lts release 4.x