NPM/Bower/Composer - 差异？ - NPM/Bower/Composer - differences?

问题：

Can someone explain to me the difference between NPM , Bower and Composer .有人可以向我解释NPM 、 Bower和Composer之间的区别吗？

They are all package managers - correct?他们都是包管理器 - 对吗？

But when should each one be used?但是什么时候应该使用每一种呢？

Also, each one appears to have a json file that accompanies it, does this store all the packages you require so they can be installed by cmd line?此外，每个似乎都有一个伴随它的 json 文件，这是否存储了您需要的所有软件包，以便它们可以通过 cmd 行安装？ Why do you need this file?为什么需要这个文件？

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解决方案：

参考： https://stackoom.com/en/question/1YA9V