##1.打开终端输入：git clone https://github.com/facebook/react-native.git下载完成后，在
目录中存在下载后的相关文件。

##2.终端输入：cd react-native && npm install
出现提示，npm command no found 因为你的mac中 npm没有安装

###npm是什么？

NPM的全称是Node Package Manager ，是一个NodeJS包管理和分发工具，已经成为了非官方的发布Node模块（包）的标准

###如何安装npm呢？
一：如果你安装了Homebrew
如何安装Homebrew见这里：http://brew.sh/index_zh-cn.html

直接使用命令：

brew install node

二：直接从官网上下载安装
点击进入网址，https://nodejs.org/en/#download

点击下载“Current”,下载完成后执行*.pkg安装完成即可。
安装完成后，就可以运行React-Native Examples下的demo了。
ps:如果通过终端命令下载不成功或是下载50%重新下载的导致下载的下载两次的如下图所示：

则需要删除目录中的react-native，否则运行demo时会出现如下错误

Failed to build DependencyGraph: @providesModule naming collision:
 Duplicate module name: AppEventsTest
 Paths: /Users/Founder/react-native/react-native/IntegrationTests/AppEventsTest.js collides with /Users/Founder/react-native/IntegrationTests/AppEventsTest.js
 This error is caused by a @providesModule declaration with the same name across two different files.
 Error: @providesModule naming collision:
 Duplicate module name: AppEventsTest
 Paths: /Users/Founder/react-native/react-native/IntegrationTests/AppEventsTest.js collides with /Users/Founder/react-native/IntegrationTests/AppEventsTest.js
 This error is caused by a @providesModule declaration with the same name across two different files.
at HasteMap._updateHasteMap (/Users/Founder/react-native/packager/react-packager/src/node-haste/DependencyGraph/HasteMap.js:155:13)
at module.getName.then.name (/Users/Founder/react-native/packager/react-packager/src/node-haste/DependencyGraph/HasteMap.js:115:31)
Process terminated. Press <enter> to close the window

如上述步骤，React-Native的demo就可以运行起来了。
参考文档：facebook_github