How to download popper.js

popper.js is used in bootstrap 4.0, but due to network reasons, dropdown may not be able to find popper.js?

dropdown The solution for popper.js cannot be found: How to download popper.js?

In the recent project, bootstrap was upgraded from version 3.3.7 to version 4.0

It was found that dropdown could not find popper.js

Solution: npm install -save popper

After downloading, check the dist directory of the node_modules file

There are two directories in the root directory, one is umd and the other is esm. In addition, there is popper.js# in the root directory.

##If it is the loading method of