How can I load d3.js with Webpacker in Rails 6?

Question

I'm trying to use d3.js in a Rails 6 app with Webpacker and I'm getting Uncaught ReferenceError: d3 is not defined.

I added d3 using yarn add d3.

My package.json file:

{
  "name": "example",
  "private": true,
  "dependencies": {
    ...
    "d3": "^5.15.0",
    ...
  },
  "version": "0.1.0",
  "devDependencies": {
    "webpack-dev-server": "^3.1.14"
  }
}

/app/javascript/packs/application.js:

require("@rails/ujs").start()
require("turbolinks").start()
require("@rails/activestorage").start()
require("channels")
require("d3")
...

In another JS file I added the following as a way to ensure it's loading properly:

...
console.log("test");
const div = d3.selectAll("div");
...

I ran rails s to restart the Rails server, then reloaded the page.

The log statement is appearing in the console but the d3 line is returning Uncaught ReferenceError: d3 is not defined.

Answer 1

You need to import d3 as a variable to be able to reference it in a Webpack-bundled JS file:

import * as d3 from "d3"

window.addEventListener('DOMContentLoaded', () => {
  d3.selectAll("div")
    .append("p")
    .text("Hello, World!")
})

Here's a demo: https://github.com/rossta/rails6-webpacker-demo/compare/example/d3