TypeScript D3 v4 import not working

Question

I am trying to build a tiny JS library on top of D3 to draw a line chart. I am fairly new to the whole scene, but I thought I'd learn best by jumping in the "deep end".

Here is the content of my package.json

{
  "name": "d3play02",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "d3-array": "^1.0.1",
    "d3-axis": "^1.0.3",
    "d3-request": "^1.0.2",
    "d3-scale": "^1.0.3",
    "d3-selection": "^1.0.2",
    "d3-shape": "^1.0.3",
    "d3-time-format": "^2.0.2",
    "rollup": "^0.36.3",
    "rollup-plugin-node-resolve": "^2.0.0",
    "uglify-js": "^2.7.4"
  },
  "dependencies": {
    "@types/d3": "^4.2.37"
  }
}

I have a file called LineChart.ts and in there I have:

/// <reference path="node_modules/@types/d3/node_modules/@types/d3-request/index.d.ts" />
import csv from 'd3-request';

class LineChart {
    data(url: string): DsvRequest {
        // code to go here
    }
}

But this is giving me an error saying this

It is complaining that it can't find the d3-request module, but I have that installed and based on the stuff I've read, I am importing correctly!

Solution

Your npm installs related to d3 should be as follows:

If you intend to use only a subset of the modules, for each module you need to install the module itself and the corresponding definition file.

E.g.: npm install d3-array --save and npm install @types/d3-array --save The actual d3-array module will be a proper dependency (not a devDependency as it appears in your snippet above). The definitions from @types may be --save or --save-dev that depends on your use case (for a library used by other code, a proper dependency should be used)

When you want to use the D3 modules with a module loader, you can then import standard TypeScript syntax:

import * as  d3Array from 'd3-array';
import {select, Selection} from 'd3-selection';

Or similar, depending on your needs.

For convenience you could create a simple "bundling" module so that you can access your custom bundle in a more consolidated form:

// d3-bundle.ts
export * from 'd3-array';
export * from 'd3-axis';
...
export * from 'd3-time-format';

You can tailor this module to your needs, including re-exporting only a subset of the members of the individual modules using export {...} from 'd3-MODULE';

In whatever module you want to use D3 now, you would import 'd3-bundle' using an appropriate relative path and you will have access to what you put through the bundle barrel:

// use-d3.ts
import { csv, DsvRequest } from './d3-bundle'; // again, use the right relative path for your project

class LineChart {
  data(url: string): DsvRequest {
      // code to go here
  }
}

Comments

[Connor Leech]

import * as d3 from "d3"; works for generic imports of the d3 library (import d3 from 'd3'; will not work)

[J86]

Thanks @tomwanzek. after doing what you suggested, VS Code can now find d3-request. However it still can't find DsvRequest! According to this the CSV function returns a DsvRequest which is defined in d3-request no?

[J86]

In fact I think something is wrong with the naming! When I did npm install @types/d3-request I got the d3-dsv typings instead of the d3-request typings!

[tomwanzek]

d3-request has a dependency on d3-dsv, the definitions have the same dependency. I just created a quick test locally by simply running npm install --save-dev @types/d3-request everything installs as expected. Note that, d3-request has convenience wrappers for e.g. getting csv or tsv data, these are not to be confused with the parsers, which are built into d3-dsv. The definitions correspond to d3-request. There are some changes in how things where done in D3 v3 compared to D3 v4.

[J86]

My bad. In VS Code when I was dong my /// <ref> I was targeting the index.d.ts within the node_modules of d3-request hence I was targeting the dependency's definition file. All good now. Thank you.