终端输入命令
defaults write com.apple.Safari IncludeInternalDebugMenu 1
重启Safari
Safari-偏好设置-高级-在菜单栏中显示“开发”菜单
https://developer.apple.com/library/safari/documentation/AppleApplications/Conceptual/Safari_Developer_Guide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40007874-CH1-SW1