Bootstrap JS not working with Rails Importmap

I have a Rails 7 App that I’m using Importmap with. I’m loading the Bootstrap JS via the gem and docs so my config/importmap.rb has:

pin "popper", to: 'popper.js', preload: true
pin "bootstrap", to: 'bootstrap.min.js', preload: true

config/initializers/assets.rb

Rails.application.config.assets.precompile += %w( bootstrap.min.js popper.js )

application.js

import 'popper'
import * as bootstrap from 'bootstrap'
document.addEventListener("turbo:load", function() {
  new bootstrap.Popover(document.getElementById('example'))
})

Stuff like dropdowns activated via data attributes work well but my custom JS gives the error: Uncaught TypeError: bootstrap.Popover is not a constructor

Answer

How to initialize Popper (tooltips) with importmaps

You’re very close. I changed your import statement for bootstrap in application.js, and modified the pin statements in importmaps to align with the documentation (linked below). Everything is working.

app/javascripts/application.js

// app/javascripts/application.js
import "@popperjs/core";
import "bootstrap";

document.addEventListener("turbo:load", function () {
  // This code is copied from Bootstrap's docs. See link below.
  var tooltipTriggerList = [].slice.call(
    document.querySelectorAll('[data-bs-toggle="tooltip"]')
  );
  var tooltipList = tooltipTriggerList.map(function (tooltipTriggerEl) {
    return new bootstrap.Tooltip(tooltipTriggerEl);
  });
});

Note, the inner code is from Bootstrap’s docs and will initialize all the tooltips on the screen.

config/importmap.rb

pin "application", preload: true
pin "@hotwired/turbo-rails", to: "turbo.min.js", preload: true
pin "@hotwired/stimulus", to: "stimulus.min.js", preload: true
pin "@hotwired/stimulus-loading", to: "stimulus-loading.js", preload: true
pin_all_from "app/javascript/controllers", under: "controllers"

# Note: Everything above was added by default. Added these two lines:
pin "bootstrap", to: "bootstrap.min.js", preload: true
pin "@popperjs/core", to: "popper.js", preload: true

The last two lines are slightly different than what you had, but are copy-pasted from the gem’s docs.

As you did, I also had to add the following:

config/initializers/assets.rb

# ... default code above ...
Rails.application.config.assets.precompile += %w( bootstrap.min.js popper.js )