我喜歡那種每過幾秒就會自動保存一次的，就像 webstorm 和 Pycharm 那樣。
VIM 我用 :help 'autosave'發現如下說明：

'autosave' 'as' number  (default 0)                                         
           ¦Automatically write the current buffer to file N seconds after the last change has been made and when 'modified' is still set.         
           ¦Default: 0 = do not autosave the buffer.                            
    Alternative: have 'autosave' use 'updatetime' and 'updatecount' but make    
    them save the file itself besides the swapfile. 

然後我就在.vimrc裡添加:set autosave as 5 ，意思應該是修改過了5秒就自動保存吧，但是它提示：Unknown option: autosave 什麼情況？