解决node与npm版本不一致，出现npm WARN npm npm does not support Node.js v15.14.0

C:\Users\user>npm -g install npm@7.7.6
npm WARN npm npm does not support Node.js v15.14.0
npm WARN npm You should probably upgrade to a newer version of node as we
npm WARN npm can't make any promises that npm will work with this version.
npm WARN npm Supported releases of Node.js are the latest release of 6, 8, 9, 10, 11, 12.
npm WARN npm You can find the latest version at https://nodejs.org/
npm ERR! code EPERM
npm ERR! syscall mkdir
npm ERR! path C:\Program Files\nodejs\node_modules\.staging
npm ERR! errno -4048
npm ERR! Error: EPERM: operation not permitted, mkdir 'C:\Program Files\nodejs\node_modules\.staging'
npm ERR!  [OperationalError: EPERM: operation not permitted, mkdir 'C:\Program Files\nodejs\node_modules\.staging'] {
npm ERR!   cause: [Error: EPERM: operation not permitted, mkdir 'C:\Program Files\nodejs\node_modules\.staging'] {
npm ERR!     errno: -4048,
npm ERR!     code: 'EPERM',
npm ERR!     syscall: 'mkdir',
npm ERR!     path: 'C:\\Program Files\\nodejs\\node_modules\\.staging'
npm ERR!   },
npm ERR!   errno: -4048,
npm ERR!   code: 'EPERM',
npm ERR!   syscall: 'mkdir',
npm ERR!   path: 'C:\\Program Files\\nodejs\\node_modules\\.staging'
npm ERR! }
npm ERR!
npm ERR! The operation was rejected by your operating system.
npm ERR! It's possible that the file was already in use (by a text editor or antivirus),
npm ERR! or that you lack permissions to access it.
npm ERR!
npm ERR! If you believe this might be a permissions issue, please double-check the
npm ERR! permissions of the file and its containing directories, or try running
npm ERR! the command again as root/Administrator.
npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\user\AppData\Roaming\npm-cache\_logs\2022-02-02T14_06_49_347Z-debug.log