JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdn.rawgit.com/mrdoob/three.js/master/build/three.min.js"></script>

CSS

body {
	  margin: 0;
}

JavaScript

let camera, scene, renderer, clock;

let curve, t = 0, speed = 0.1;

const point = new THREE.Vector3();

init();
animate();

function init() {

    camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 0.01, 10 );
    camera.position.z = 1;

    scene = new THREE.Scene();
    clock = new THREE.Clock();

    const geometry = new THREE.BoxGeometry( 0.2, 0.2, 0.2 );
    const material = new THREE.MeshNormalMaterial();

    const mesh = new THREE.Mesh( geometry, material );
    scene.add( mesh );
    
    curve = new THREE.LineCurve3( 
    	new THREE.Vector3( 0.2, 0.2, 0 ),
      new THREE.Vector3( 1, 1, 0 )
    );

    renderer = new THREE.WebGLRenderer( { antialias: true } );
    renderer.setSize( window.innerWidth, window.innerHeight );
    document.body.appendChild( renderer.domElement );

}

function animate() {

    requestAnimationFrame( animate );
    
    t += clock.getDelta() * speed;

    curve.getPointAt( t % 1, camera.position ); // t % 1 means we only use the fractional part of the number
    
    camera.lookAt( scene.position );

    renderer.render( scene, camera );

}