我npm install gulp在 Ubuntu 中运行。显示此错误：
我的服务器是 Ubuntu 16.04。
框架是 Laravel 5.6。
ERROR: npm is known not to run on Node.js v4.2.6
Node.js 4 is supported but the specific version you're running has
a bug known to break npm. Please update to at least 4.7.0 to use this
version of npm. You can find the latest release of Node.js at https://nodejs.org/
我运行node -v显示此消息：v4.2.6
我运行sudo apt-get install --only-upgrade nodejs显示此消息：
Reading package lists... Done
Building dependency tree
Reading state information... Done
nodejs is already the newest version (9.11.1-1nodesource1).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
nodejs已经是最新版本(9.11.1-1nodesource1)。
删除后nodejs，我运行node -v，显示消息：4.2.6!!!! 但是上面的消息已经删除了版本 9！
如何删除 nodejs 版本 4.2.6 ？如何解决这个问题？