Node.js 在 OSX 中安装 npm 模块时权限被拒绝

我正在try 安装node-g.raphael，但出现以下错误:

Bender-03:htdocs alfred$ sudo npm install node-g.raphael --save
Password:

> contextify@0.1.15 install 
  /Users/alfred/Sites/twistedgeo/htdocs/node_modules/contextify
> node-gyp rebuild

gyp ERR! configure error
gyp ERR! stack Error: EACCES: permission denied, mkdir 
  '/Users/alfred/Sites/twistedgeo/htdocs/node_modules/contextify/build'
gyp ERR! System Darwin 16.7.0
gyp ERR! command "/usr/local/bin/node" 
  "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" 
  "rebuild"
gyp ERR! cwd 
  /Users/alfred/Sites/twistedgeo/htdocs/node_modules/contextify
gyp ERR! node -v v8.8.1
gyp ERR! node-gyp -v v3.6.2
gyp ERR! not ok
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: contextify@0.1.15 
  (node_modules/contextify):
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: contextify@0.1.15 
  install: `node-gyp rebuild`
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: Exit status 1

+ node-g.raphael@0.0.9
added 2 packages and updated 1 package in 6.556s

我试了this solution次，但还是没有解决我的问题，还是出现了同样的错误.

如果有什么可以帮助解决的，请告诉我.