threejs/app/js/index.js

import * as THREE from 'three';

var renderer = new THREE.WebGLRenderer();
renderer.setSize( window.innerWidth, window.innerHeight );
document.body.appendChild( renderer.domElement );

var camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 500 );
camera.position.set( 0, 0, 100 );
camera.lookAt( 0, 0, 0 );

var scene = new THREE.Scene();

var material = new THREE.LineBasicMaterial( { color: 0x0000ff } );

var points = [];
points.push( new THREE.Vector3( - 10, 0, 0 ) );
points.push( new THREE.Vector3( 0, 10, 0 ) );
points.push( new THREE.Vector3( 10, 0, 0 ) );

var geometry = new THREE.BufferGeometry().setFromPoints( points );

var line = new THREE.Line( geometry, material );


scene.add( line );
renderer.render( scene, camera );