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Importing leaflet into module from cdn with typescript support

I'm trying to import leaflet into a javascript module with typescript support but can't get it to work.
I've installed #types/leaflet and have tried to following:
import 'https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.8.0/leaflet.js'
This works fine in the browser but typescript gives the following error:
'L' refers to a UMD global, but the current file is a module. Consider adding an import instead.ts(2686)
(I call L.map() in my code)
I've also tried:
import * as L from 'https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.8.0/leaflet.js'
This works fine in typescript, but gives the following error in chrome:
Uncaught TypeError: L.map is not a function
Anyone know how to fix this?
I don't want to use a bundler.
Edit
As jsejcksn suggested in the comments, importing a ES module version of leaflet and adding a path alias to typescript fixed this.
I'm now using the following import:
import * as L from 'https://unpkg.com/leaflet#1.8.0/dist/leaflet-src.esm.js'
The problem with this though, as stated on Leaflet's Download page, is that this imports Leaflet's source files including unit tests, files for debugging, build scripts, etc. This doesn't seem very efficient to me.
Any other ideas?
Edit 2
It seems like Leaflet 1.9 will solve my problem when it will be released. This pull request adds an ES module entrypoint to Leaflet meaning you can do this:
import L from 'leaflet'
or in our case:
import L from 'cdn.com/link/to/leaflet/1.9/esm'
In the mean time, jsejcksn's answer provides a good alternative so I will accept that answer.

Preface
I've already written an answer about how to do this with ES modules at the question How to include modules in client side in typescript projects?. Be sure to read through that question and answer for context here.
You said:
I don't want to use a bundler.
and also:
The problem with this though, as stated on Leaflet's Download page, is that this imports Leaflet's source files including unit tests, files for debugging, build scripts, etc. This doesn't seem very efficient to me.
These ideas seem at odds to me. Without more information, I can only assume that by "not very efficient" you mean that the byte size of the presumably not-tree-shaken ES module is larger than the UMD module. If that's the case, why not just import Leaflet into your bundle and tree-shake away all of the parts that you don't use during build, resulting in even fewer bytes than the UMD?
Ignoring that for now, and responding purely to your stated criteria, below I will provide a self-contained, reproducible example demonstrating how you can use a CDN-hosted UMD module that has a corresponding #types package in a TypeScript ES module without augmenting the definition of globalThis.window in the compiler and without bundling.
Note that some of what I show will be purely ceremonial, but the technique will allow for you to later swap out the shim module URL in the import map with a CDN ES module URL if/when you find one that suits you.
Download the files in this example
I'm going to provide a complete reproducible example here, including all the content of each file in a code block. If you want to use this example to reproduce it and don't want to copy + paste every individual code block into a new file with a matching name on your device, then you can copy + paste the following script and run it in your browser console to download the repo as a zip archive file:
function download (data, fileName, mediaType) {
const a = document.createElement('a');
const blob = new Blob([data], mediaType ? {type: mediaType} : undefined);
const url = URL.createObjectURL(blob);
a.href = url;
a.download = fileName;
a.click();
a.remove();
// URL.revokeObjectURL(url);
}
download(
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"so-73091042.zip",
"application/zip",
);
Example
This example will be served using a static file server from the ./public directory, and the entrypoint html file is here:
./public/index.html:
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>Stack Overflow 73091042</title>
<!-- First, define an import map for the "leaflet" module specifier
which points to the UMD-to-ESM shim module: -->
<script type="importmap">
{
"imports": {
"leaflet": "/leaflet_umd_shim.js"
}
}
</script>
<!-- Then, import the entrypoint module: -->
<script type="module" src="/main.js"></script>
</head>
<body>
<h1>See console output</h1>
</body>
</html>
Nothing special there except maybe the import map if you aren't familiar: WICG/import-maps: How to control the behavior of JavaScript imports
Next, there are two TypeScript source files in the ./src directory which are transpiled to JavaScript and copied into the ./public directory during compilation.
The first is a shim:
./src/leaflet_umd_shim.ts:
// Creates a proxy to the UMD Leaflet object `window.L` as a type-safe ESM export
/*
This loads (and executes) the UMD Leaflet script the first time that
this module is imported into the module graph, which assigns
the UMD Leaflet object to `window.L`. This is scope pollution, and is
one of the things that ES modules avoid, but is necessary here because
you expressed dissatisfaction at the available Leaflet ES module options
at existing CDN URLs.
This proxy technique "works" well here because Leaflet
is an object export/namspace and is documented to be used this way. However,
note that — for other modules which provide multiple exports that are
intended to be imported individually by name — this technique wouldn't be
a good fit because it requires the entire UMD module to be made available
on a single (named) export. (Note that the default export is just a named export
using the name "default").
*/
import 'https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.8.0/leaflet.js';
import type * as Leaflet from 'leaflet';
const {L} = window as unknown as { L: typeof Leaflet };
// Same as `export {L as default}`:
export default L;
The "leaflet" import specifier in the import map is bound to the location of the JavaScript module produced by this file during compilation.
That specifier is used in the entrypoint module:
./src/main.ts:
/*
(Reference comments in "leaflet_umd_shim.ts" for context)
Example of non-working named import:
import {tileLayer} from 'leaflet';
It would throw the following runtime exception:
"Uncaught SyntaxError: The requested module 'leaflet' does not provide
an export named 'tileLayer'"
This technique requires importing the entire UMD module on a name (even if that
name is "default"):
*/
// Same as `import {default as L} from 'leaflet'`:
import L from 'leaflet';
const a = L.latLng(50.5, 30.5);
const b = L.latLng(51.5, 30.5);
const distance = a.distanceTo(b);
console.log({a, b, distance}); /* Prints the following:
{
"a": {
"lat": 50.5,
"lng": 30.5
},
"b": {
"lat": 51.5,
"lng": 30.5
},
"distance": 111194.92664455874
}
*/
When you serve this site on a local http server and access the HTML file, the main module will execute and print that information to the console using those methods from Leaflet to create the data that is logged, proving that this technique works.
Here's my TSConfig:
./tsconfig.json:
{
"compilerOptions": {
// Strict options (This is TS: type safety is important)
"exactOptionalPropertyTypes": true,
"isolatedModules": true,
"noUncheckedIndexedAccess": true,
"strict": true,
"useUnknownInCatchVariables": true,
// ESM
"esModuleInterop": true,
"module": "esnext",
"moduleResolution": "nodenext",
"lib": [
"esnext", // Latest ES syntax features
"dom", // Browser runtime environmnt
"dom.iterable" // Browser runtime environmnt
],
"target": "esnext", // Adjust this to your browser target needs
"outDir": "public", // Directory from which the site will be served
// Path mapping
// Ref: https://www.typescriptlang.org/docs/handbook/module-resolution.html#path-mapping
"baseUrl": ".",
"paths": {
"leaflet": ["node_modules/#types/leaflet"]
},
// Optional settings
"removeComments": true
},
"include": ["src/**/*"]
}
And, lastly, here's the npm package file:
./package.json:
{
"name": "so-73091042",
"version": "0.1.0",
"type": "module",
"scripts": {
"compile": "tsc",
"serve": "static --port=8000 --cache=false public"
},
"license": "MIT",
"devDependencies": {
"#types/leaflet": "^1.7.11",
"node-static": "^0.7.11",
"typescript": "^4.7.4"
},
"volta": {
"node": "16.16.0"
}
}
You can ignore the volta property: it just shows that I was using Volta and the version of Node that I had installed when creating this repository example.
The node-static dependency is the package recommended by the official Node.js website for serving static files in the article How to serve static files | Node.js.
First use npm install to install the dependencies:
% npm install
added 9 packages, and audited 10 packages in 4s
Then — to compile the TS files and emit them — use npm run compile:
% npm run compile
> so-73091042#0.1.0 compile
> tsc
There should now be two new files in the ./public directory after compilation:
./public/leaflet_umd_shim.js:
import 'https://cdnjs.cloudflare.com/ajax/libs/leaflet/1.8.0/leaflet.js';
const { L } = window;
export default L;
./public/main.js:
import L from 'leaflet';
const a = L.latLng(50.5, 30.5);
const b = L.latLng(51.5, 30.5);
const distance = a.distanceTo(b);
console.log({ a, b, distance });
Now everything is ready to be served by the static file server, so use the command npm run serve:
% npm run serve
> so-73091042#0.1.0 serve
> static --port=8000 --cache=false public
serving "public" at http://127.0.0.1:8000
If you navigate to http://127.0.0.1:8000 in your browser (this is the same as http://localhost:8000), you'll see the index page with the text "See console output", and if you look at your browser's JS console, you'll see a representation of the object data that was logged to the console in the main.js module.
When you're ready to stop the server, just use ctrl + c in your terminal
And that's it!

How to use TypeScript w/ a library with no definition file?

So I’m trying to use the pino-clf library in my koa TS project.
I keep getting this when I try to compile:
TSError: ⨯ Unable to compile TypeScript:
src/modules/logger/index.ts:5:21 - error TS7016: Could not find a declaration file for module 'pino-clf'. '/dev/webservices/node_modules/pino-clf/index.js' implicitly has an 'any' type.
Try `npm i --save-dev #types/pino-clf` if it exists or add a new declaration (.d.ts) file containing `declare module 'pino-clf';`
5 import pinoClf from 'pino-clf'
~~~~~~~~~~
pino-clf doesn’t have a def file and there’s no #types/pino-clf available.
I tried adding a pino-clf.d.ts file in the folder of the file that I’m importing the lib into w/ declare module 'pino-clf' in it. While that got the red squigglies in my IDE to go away, TS still refuses to compile.
How in the world do we use use a lib that’s just plain JS w/ TS and w/o adding a ts-ignore?

So there are two ways this can be accomplished.
Solution One: Probably the easiest
You can just use require ex: const pinoClf = require("pinoClf") - the down-side is that dot reference or intellisense isn't available but if you know the methods you want to use its no biggie.
Solution Two:
Create you own typeDef file in the root of you project. For example,
pino-clf.custom.d.ts
declare module "pino-clf.custom" {
const pinoClfJs = require("pinoClf");
export default class pinoClf {
commonLog (type: string, dest: NodeJS.WriteStream, ancillary: any): void {
pinoClfJs.commonLog(type, dest, ancillary);
}
}
}
then in you tsconfig.json file include the new typeDef file:
{
... // assuming src is already there
"include": [
"src", "pino-clf.custom.d.ts"
]
}
after that you can simply import it import pinoClf from "pino-clf.custom";
This is a very basic implementation, and recommend researching if you desire something more complex. Of course there is more than one way to solve a problem but, I hope this helped. Cheers.

Javascript modules - Cannot use import statement outside a module

I am new to Javascript and I am trying to learn modules from a tutorial. In have a folder in visual studio code/VScode which has two files, script.js & external.js.
Script.js imports content from external.js and prints text to console. I get the below error when I run script.js from vs code, with node.js run configuration. Can someone please tell me why this happens and how to fix it ? In comparison, imports in Java are simple.
import {keyValue} from './external.js';
^^^^^^
SyntaxError: Cannot use import statement outside a module
at wrapSafe (internal/modules/cjs/loader.js:1070:16)
at Module._compile (internal/modules/cjs/loader.js:1120:27)
external.js :
export let keyValue = 1000;
script.js :
import {keyValue} from './external.js';
console.log(keyValue);
UPDATES :
Node version - v12.16.2, upgraded to v14.4.0.

What's the version of node.js?
If node.js is version 13 or above, you can do either:
add { type: "module" } to package.json.
{
...
scripts: "...",
type: "module"
}
rename .js to .mjs
If it's under 13, rename .js to .mjs, and run with additional params --experimental-modules.
node --experimental-modules script.js
Or
You can also fix the import statement outside a module issue
by not using the import statement and using the dynamic import function instead.
script.js
import("./external.js").then((module) => {
console.log(module.keyValue);
});
This form also supports the await keyword.
let module = await import('./external.js');
console.log(module.keyValue)

it's because you are using es6 modules instead of the default module system for node which is common js. you could either use babel to transpile it or to use the .mjs extension

TypeScript "import { myVar }" syntax seems to be incorrectly compiling in a Node/CommonJS/ES5 app

In my Node application, I have a settings file that exports some settings as an object like this:
// settings.ts
export var settings = {
port: 1234
}
In another file, I import these settings and attempt to reference the port property:
// another-file.ts
import { settings } from './settings';
console.log(settings.port);
This code compiles correctly, but at runtime I get the following error:
Cannot read property 'port' of undefined
When I inspect the compiled code, I can see that this is happening because my second file above is compiling to this:
var settings_1 = require("./settings");
console.log(settings_1.settings.port);
If I walk through the compiled code with my debugger, I can see that the settings_1 variable points to the exported value from settings.ts. In other words, my port property lives at settings_1.port, not at settings_1.settings.port. It seems the TypeScript compiler should instead generated this JavaScript code:
var settings = require("./settings");
console.log(settings.port);
Am I doing something wrong? Or is the TypeScript compiler incorrectly compiling my import?
I know that the TypeScript compiler is correctly type-checking my import; if I do something like this:
import { settings } from './settings';
console.log(settings.propertyThatDoesNotExist);
I get compiler errors that propertyThatDoesNotExist doesn't exist.
I'm using TypeScript 2.3.2, targeting "es5" and outputting "commonjs" modules, running on Node 6.9.2.

Figured it out. It was a silly mistake on my part (isn't it always?). I was working on converting an application from JavaScript to TypeScript, and I copied and renamed settings.js to settings.ts... but I didn't delete settings.js. As a result, I was actually importing my old settings.js file which had its exports set up differently.
Once I deleted settings.js, my application started correctly using the .ts file instead, and my imports worked as expected.

How to import from nested module?

I have a Typescript library I've written which is being emitted as follows. I'm not sure how to import from this module, though.
node_modules/my-module/dist/index.js (partial)
define("services/UserService", ["require", "exports", ..., "services/BaseService"], function (require, exports, ..., BaseService_31) {
"use strict";
var UserService = (function (_super) {
// ... stuff here ...
return UserService;
}(BaseService_31.BaseService));
exports.UserService = UserService;
});
I've installed this package with npm and configured JSPM as follows:
config.js (partial)
System.config({
defaultJSExtensions: true,
transpiler: "none",
paths: {
"*": "dist/*",
"github:*": "jspm_packages/github/*",
"npm:*": "jspm_packages/npm/*",
"npm-ext:*": "node_modules/*"
},
map: {
...
"my-module": "npm-ext:my-module/dist/index.js",
...
}
});
I was expecting to be able to import this class as follows...
import {UserService} from "my-module/services/UserService";
I expected SystemJS to resolve the path to my-module and then locate the services/UserService module, and grab the single export UserService. But in the Chrome Console I see this is the path which is being loaded:
node_modules/my-module/dist/index.js/models/UserService.js
What's the correct way to import a module such as this?
Bonus: how can I get around including the full path to index.js?

Your library code was emitted using named define
define("services/UserService",
And it looks like there are several such modules defined in the index.js file, that is, index.js is a bundle.
The only way to import such module using SystemJS is
import {UserService} from "services/UserService";
That is, imported module name must match exactly the name given to define. In your case, the location of the file does not affect module name in any way.
Now, SystemJS has to be configured to load library file, node_modules/my-module/dist/index.js, when it sees that import. For bundles, the preferred way to to it is via bundles config:
bundles: {
"npm-ext:my-module/dist/index.js": ["services/UserService.js"]
}
Module name here, services/UserService.js, must have .js extension because it must match imported module name after defaultJSExtesions:true is applied.
If you want the module to be imported as my-module/services/UserService.js, then you need to make sure it is registered with that name. The easiest way is to have corresponding source file structure when compiling the library - that is, have UserService.ts in my-module/services folder.
You can find more information about named define in SystemJS module format docs, which says in particular
Named defines are supported and will write directly into the loader registry.
A single named define will write into the loader registry but also be treated as the value of the module loaded if the names do not match. This enables loading a module containing define('jquery', ....
P.S. Your browser tries to load
node_modules/my-module/dist/index.js/models/UserService.js
where does models come from?