JSFiddle - React, Tailwind, and code Playground

CSS

body {
	  margin: 0;
}

JavaScript

import * as THREE from 'https://cdn.jsdelivr.net/npm/three@0.121.1/build/three.module.js';
import { OrbitControls } from 'https://cdn.jsdelivr.net/npm/three@0.121.1/examples/jsm/controls/OrbitControls.js';

var camera, scene, renderer;
var cube_geom, material, mesh;

init();
animate();

function init() {

    camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 0.01, 10 );
    camera.position.set( 1, 0, 0 );

    scene = new THREE.Scene();

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

		cube_geom.faces = [ cube_geom.faces[ 0 ], cube_geom.faces[ 1 ] ];
		cube_geom.mergeVertices();
    
    //---------------- my code -----------------------------------------------------
    var to_remove = [0,1,2,3,4,5,6,7];
    //console.log(cube_geom.faces)
    
    for(var key in cube_geom.faces){
        for(var key2 in to_remove){
            if(cube_geom.faces[key].a == to_remove[key2]) to_remove.splice(key2,1);
            if(cube_geom.faces[key].b == to_remove[key2]) to_remove.splice(key2,1);
            if(cube_geom.faces[key].c == to_remove[key2]) to_remove.splice(key2,1);
        }
    }

    for(var k in to_remove){

        //if(to_remove[k] == 7 && k==2) break //console.log(k)
        cube_geom.vertices.splice([to_remove[k]-k],1);
        
        for(var key in cube_geom.faces){

            if(cube_geom.faces[key].a >= to_remove[k]-k) cube_geom.faces[key].a--;
            if(cube_geom.faces[key].b >= to_remove[k]-k) cube_geom.faces[key].b--;
            if(cube_geom.faces[key].c >= to_remove[k]-k) cube_geom.faces[key].c--;
        } 
    }
    //-------------------- end my code -------------------------------------
		console.log( cube_geom.vertices.length );

    mesh = new THREE.Mesh( cube_geom, material );
    scene.add( mesh );

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