Howto make no-depends widget on Svelte and load it on the page

widget.md

We should have at least three files: 'Widget.svelte', 'rollup.config.js' and 'package.json':

1. Our widget Widget.svelte:

<script>
	export let name;
</script>

<h1>Hello {name}!</h1>

<style>
	h1 {color: red;}
</style>

2. Our rollup.config.js:

import svelte from 'rollup-plugin-svelte';
import resolve from 'rollup-plugin-node-resolve';
import commonjs from 'rollup-plugin-commonjs';
import { terser } from 'rollup-plugin-terser';

export default {
	input: './Widget.svelte',
	output: {
		format: 'iife',
		name: 'MyWidget', // Name of the class we will call on the page
		file: 'dist/mywidget.js' // the file which we will include on the page
	},
	plugins: [
		svelte({
			emitCss: false  // Let's store CSS in JS (no-depends), but you can emit it in separate *.css file too
		}),
		resolve({
			browser: true,
			dedupe: importee => importee === 'svelte' || importee.startsWith('svelte/')
		}),
		commonjs(),
		terser()
	]
};

3. And our package.json file:

{
  "devDependencies": {
    "rollup": "^1.12.0",
    "rollup-plugin-commonjs": "^10.0.0",
    "rollup-plugin-node-resolve": "^5.2.0",
    "rollup-plugin-svelte": "^5.0.3",
    "rollup-plugin-terser": "^5.1.2",
    "svelte": "^3.0.0"
  },
  "scripts": {
    "build": "rollup -c"
  }
}

4. Run 'npm i' to install all dependencies.

5. Run 'npm run build' to compile our widget to the single mywidget.js file in the dist directory

6. Then you can include that file on any HTML page and it will work.

...
<div id="mywidget"></div>
<script src='mywidget.js'></script>
<script>
new MyWidget({
	target: document.getElementById("mywidget"),
	props: {
		name: 'world'
	}
});
</script>
 ...