另一方面，npx使用的包并不是全局安装的，所以你必须担心长期的污染。

简单的定义:

Javascript包管理器

npx -执行npm包的二进制文件

npx是一个npm包运行器(x可能代表eXecute)。使用npx的一种常见方法是下载并临时运行一个包或进行试用。

Create-react-app是一个NPM包，预计在项目的生命周期中只运行一次。因此，最好使用npx在一个步骤中安装和运行它。

正如主页https://www.npmjs.com/package/npx中提到的，默认情况下，npx可以在PATH或node_modules/.bin中运行命令。

注意: 通过深入研究，我们可以发现create-react-app指向一个在节点环境中执行的Javascript文件(在Linux系统中可能是/usr/lib/node_modules/create-react-app/index.js)。这只是一个执行一些检查的全局工具。实际的设置由react-scripts完成，其最新版本安装在项目中。更多信息请参考https://github.com/facebook/create-react-app。

NPM vs NPX

NPM代表节点包管理器。一个基于文本的Nodejs包管理程序。

而NPX是一个节点包运行器。它的功能是执行Nodejs包

NPX将执行Nodejs包中的二进制文件，无论是否安装。

甚至NPX也可以帮助我们使用某些版本的Nodejs，而不必使用nvm (node.js版本管理)、nave (node.js虚拟环境)和nvm (node.js版本管理)。

NPX:

从https://www.futurehosting.com/blog/npx-makes-life-easier-for-node-developers-plus-node-vulnerability-news/:

Web developers can have dozens of projects on their development machines, and each project has its own particular set of npm-installed dependencies. A few years back, the usual advice for dealing with CLI applications like Grunt or Gulp was to install them locally in each project and also globally so they could easily be run from the command line. But installing globally caused as many problems as it solved. Projects may depend on different versions of command line tools, and polluting the operating system with lots of development-specific CLI tools isn’t great either. Today, most developers prefer to install tools locally and leave it at that. Local versions of tools allow developers to pull projects from GitHub without worrying about incompatibilities with globally installed versions of tools. NPM can just install local versions and you’re good to go. But project specific installations aren’t without their problems: how do you run the right version of the tool without specifying its exact location in the project or playing around with aliases? That’s the problem npx solves. A new tool included in NPM 5.2, npx is a small utility that’s smart enough to run the right application when it’s called from within a project. If you wanted to run the project-local version of mocha, for example, you can run npx mocha inside the project and it will do what you expect. A useful side benefit of npx is that it will automatically install npm packages that aren’t already installed. So, as the tool’s creator Kat Marchán points out, you can run npx benny-hill without having to deal with Benny Hill polluting the global environment. If you want to take npx for a spin, update to the most recent version of npm.

另一方面，npx使用的包并不是全局安装的，所以你必须担心长期的污染。