Can not use toast of bootstrap in rails

I did yarn add bootstrap jquery popper.js and import bootstrap into the app.
Also, bootstrap's popover and tooltip style works well.
But when I add a toast in page and run $('div.toast').toast('show') in chrome's console, it says $(...).toast is not a function
Do you know what's wrong?

Sounds like you missed a step. I just updated the repository to include toasts in the example and they work just fine.

https://github.com/gorails-screencasts/bootstap-with-webpack-4/commit/49846a028f0d6674b0024fbd4c1f6051c8757884

Compare your code with the repository and see what you missed.