遇到的问题：
根据官方文档github.com/nvm-sh/nvm在命令行中输入下面命令：
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
出现错误：
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0curl: (7) Failed to connect to raw.githubusercontent.com port 443: Connection refused
解决办法：
访问地址：github.com/nvm-sh/nvm，将install.sh下载到本地，保存位置自定。
进入文件保存位置，执行./install.sh文件
cd Desktop/
./install.sh
在执行./install.sh文件时可能会出现下面这种问题：
-bash: ./install.sh: Permission denied
执行下面命令：
chmod 777 install.sh
./install.sh
=> Downloading nvm from git to '/Users/liuxing/.nvm'
=> Cloning into '/Users/liuxing/.nvm'...
remote: Enumerating objects: 290, done.
remote: Counting objects: 100% (290/290), done.
remote: Compressing objects: 100% (257/257), done.
remote: Total 290 (delta 35), reused 97 (delta 20), pack-reused 0
Receiving objects: 100% (290/290), 163.27 KiB | 4.00 KiB/s, done.
Resolving deltas: 100% (35/35), done.
=> Compressing and cleaning up git repository
=> Appending nvm source string to /Users/liuxing/.bash_profile
=> Appending bash_completion source string to /Users/liuxing/.bash_profile
=> Close and reopen your terminal to start using nvm or run the following to use it now:
export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh" # This loads nvm
[ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion" # This loads nvm bash_completion
此时输入nvm会提示找不到该命令：
-bash: nvm: command not found
关掉终端重新打开就可以了。接下来就可以用nvm来安装指定版本的node和npm了：
nvm install v10.15.3
