title: npm: How to reset the node_modules prefix
body: <p>i installed node via homebrew. 
  Since i had problems accessing the packages, i tried to change the node_modules prefix to <code>user/local</code> but made an error while typing the command:</p>
  
  <pre><code>npm config set prefix /usr/l    # See the typo there
                              ^
  </code></pre>
  
  <p>Now, whenever i run an npm command i get the following error: </p>
  
  <pre><code>$ npm config ls -l
  Error: EACCES: permission denied, mkdir '/usr/l'
  at Error (native)
  </code></pre>
  
  <p>i cannot set the prefix again (<code>npm config set prefix /usr/local</code>) , or even list the config ( <code>npm config ls -l</code> ) – all produce the same error as above.  I tried re-installing node/npm.</p>
  
  <p>How do i reset the prefix? Thanks.  </p>