Create a basic GLB with a single mesh.

create-basic-glb.js

import { Accessor, Document, Primitive, NodeIO } from '@gltf-transform/core';

const document = new Document();
const prim = document.createPrimitive();
const buffer = document.createBuffer();

const material = document.createMaterial()
    .setBaseColorFactor([1.0, 0.0, 0.0, 1.0])
    .setMetallicFactor(0.0)
    .setRoughnessFactor(1.0);

prim.setMode(Primitive.Mode.TRIANGLES)
    .setMaterial(material)
    .setAttribute(
        'POSITION',
        document
            .createAccessor()
            .setArray(new Float32Array([0, 0, 0]))
            .setType(Accessor.Type.VEC3)
            .setBuffer(buffer)
    )
    .setAttribute(
        'COLOR_0',
        document
            .createAccessor()
            .setArray(new Uint8Array([128, 128, 128]))
            .setType(Accessor.Type.VEC3)
            .setBuffer(buffer)
    );

const mesh = document.createMesh().addPrimitive(prim);
const node = document.createNode().setMesh(mesh);
const scene = document.createScene().addChild(node);

const io = new NodeIO();
await io.write('path/to/output.glb', document);