a three.js boilerplate scene in a single 30 line self-contained html file

three.html

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/reset-css@5.0.1/reset.min.css">
<script type="module">
import * as THREE from "https://cdn.jsdelivr.net/npm/three@0.124.0/build/three.module.js"
import { OrbitControls } from "https://cdn.jsdelivr.net/npm/three@0.124.0/examples/jsm/controls/OrbitControls.js"

var scene = new THREE.Scene()

var camera = new THREE.PerspectiveCamera(75)
camera.position.z = 4

var renderer = new THREE.WebGLRenderer()
document.body.appendChild(renderer.domElement)

window.onresize = function () {
    camera.aspect = window.innerWidth / window.innerHeight
    camera.updateProjectionMatrix()
    renderer.setSize(window.innerWidth, window.innerHeight)
}
window.onresize()

scene.add(new THREE.GridHelper(10, 10))
new OrbitControls(camera, renderer.domElement)

function render() {
    requestAnimationFrame(render)
    renderer.render(scene, camera)
}

render()
</script>