Hemant Vishwakarma: How to get the Chart.js type information into my plain javascript file using JSDoc?

Sunday 19 November 2023

How to get the Chart.js type information into my plain javascript file using JSDoc?

I can't seem to get JSDoc-based intellisense in VSCode to work for the Chart.js library.

Reproducible scenario

The steps are minimal and detailed below, but you can also clone my repository created with the steps from this question.

I have a rather old application, here's a minimally reproducible variant of what I have:

Run npm i chart.js chartjs-adapter-moment moment
Create an index.html like this:

<html>
  <script src="node_modules/moment/moment.js"></script>
  <script src="node_modules/chart.js/dist/chart.umd.js"></script>
  <script src="node_modules/chartjs-adapter-moment/dist/chartjs-adapter-moment.js"></script>
  <script src="app.js"></script>
  <div style="height: 200px; width: 300px;"><canvas id="my-chart"></canvas></div>
</html>

Create an app.js file like this:

// @ts-check

/**
 * @typedef moment
 * @property {import('moment')} moment
 */

/**
 * @global {import('chart.js')} Chart
 */

document.addEventListener("DOMContentLoaded", () => {
  const ctx = document.getElementById("my-chart");
  const chartRef = new Chart(ctx, {
    type: "line",
    options: {
      scales: {
        x: { type: "time" },
        y: { min: 0, max: 10 },
      },
    },
    data: {
      datasets: [
        {
          label: 'Stuff',
          data: [
            { x: moment("2023-01-01"), y: 2 },
            { x: moment("2023-02-01"), y: 8 },
            { x: moment("2023-03-01"), y: 3 },
            { x: moment("2023-04-01"), y: 6 },
          ],
        },
      ],
    },
  });
});

The problem

The moment types seem to be working well in VSCode. But the Chart typings are not working at all. Here's what it does in VSCode currently:

I've tried a bunch of different things instead of the @global declaration, nothing seems to work.

Bottom line / The question

How do I properly get the type completion for Chart.js Chart and related types in VSCode when I'm not using any import or require or similar?

Things I've tried

A helpful answer appeared but I can add the suggestions from it to the "things I've tried", but they don't fix my specific issue as detailed below.

The first suggestion was to use /** @typedef {import("chart.js")} */ but that leaves me with the same error:

Cannot find name 'Chart'. ts(2304)

As I wrote in my comment to the answer at some point I think I also saw:

'Chart' only refers to a type, but is being used as a value here. ts(2693)

But I must've gotten that on a slight variation to the suggestion, and can't seem to get that specific error now anymore.

An edit to the question was made to suggest trying /** @typedef {import("chart.js").Chart} Chart */ which does give me:

'Chart' only refers to a type, but is being used as a value here. ts(2693)

As you can tell from the corresponding screenshot:

from How to get the Chart.js type information into my plain javascript file using JSDoc?

Hemant Vishwakarma