如何在three.js中一次仅加载一个模型？

<script src="https://cdn.jsdelivr.net/npm/three@0.132.0/build/three.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/three/examples/js/loaders/GLTFLoader.js"></script>

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
var renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

var loader = new THREE.GLTFLoader();
loader.load('model.gltf', function (gltf) {
    scene.add(gltf.scene);
}, undefined, function (error) {
    console.error(error);
});

camera.position.z = 5;

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