Cannot get GitLab CI to build my Middleman/Gulp project - node.js

Question

I am using Gitlab-CI to build my Middleman application which also uses some node stuff for the front end (Gulp).
Here is my .gitlab-ci.yml (mostly copied from here):
image: ruby:2.3
cache:
paths:
- vendor
- node_modules
before_script:
- apt-get update -yqqq
- apt-get install -y npm
- ln -s /usr/bin/nodejs /usr/bin/node
- npm install
- bundle install --path vendor
test:
script:
- bundle exec middleman build
except:
- master
pages:
script:
- bundle exec middleman build
artifacts:
paths:
- public
only:
- master
Everything goes alright apart from the vital problem that it seems to be using an old version of node when it's npm installing. I'm getting lots of this:
npm WARN engine gulp-babel#7.0.0: wanted: {"node":">=4"} (current: {"node":"0.10.29","npm":"1.4.21"})
Before finally failing on the "const path" SyntaxError.
I included a line to symlink the new nodejs with the old name (- ln -s /usr/bin/nodejs /usr/bin/node) but it seems to have no effect...?
Been banging my head for long enough, there's got to be someone out there who has made this work?

Answer 1

Debian Jessie ships with a fixed NodeJs major version, follow NodeSource instructions to install a specific version, this would fit in your gitlab-ci.yml like this (you probably need to install curl first since its not installed in the ruby:2.3 image):
before_script:
- apt-get update -q && apt-get -qqy install curl
- curl -sL https://deb.nodesource.com/setup_9.x | bash -
- apt-get update -q && apt-get -qqy install nodejs npm
- ln -s /usr/bin/nodejs /usr/bin/node
- npm install
- bundle install --path vendor