To quit (close) a Mac app normally, choose Quit from the app's menu in the menu bar, or press Command (⌘)-Q. If the app doesn't quit, follow these steps to force the app to quit.

How to force an app to quit

Update from 09/2017. It is possible to develop iOS (and Android at the same time) application using React Native + Expo without owning a mac. You will also be able to run your iOS application within iOS Expo app while developing it. (You can even publish it for other people to access, but it will only run within Expo app). Here's how to completely close the program with Windows' Task Manager or Mac OS X's Force Quit. Every computer user at some point will likely have to deal with a program that just stops responding.

1. Press these three keys together: Option, Command, and Esc (Escape). This is similar to pressing Control-Alt-Delete on a PC. Or choose Force Quit from the Apple () menu in the upper-left corner of your screen.
   
2. Select the app in the Force Quit window, then click Force Quit.
   

Learn more

Exit A Non Responding App On Mac Computer

Exit A Non Responding App On Mac

• You can also force the Finder to quit, if it stops responding. Select Finder in the Force Quit window, then click Relaunch.
• If none of your apps are responding, you can force your Mac to restart.
• You can also force an app to close on your iPhone, iPad, or iPod touch.