MeshAttributeAccessor

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  const mesh = this.object.getComponent('mesh').mesh;
  const positions = mesh.attribute(WL.MeshAttribute.Position);

  const temp = new Float32Array(3);
  for(int i = 0; i < positions.length; ++i) {
      // pos will reference temp and thereby not allocate additional
      // JavaScript garbage, which would cause a perf spike when collected.
      const pos = positions.get(i, temp);
      // scale position by 2 on X axis only
      pos[0] *= 2.0f;
      positions.set(i, pos);
  }
  // we're done modifying, tell the engine to move vertex data to the GPU
  mesh.update();

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const vertexCount = 4;
const positionAttribute = mesh.attribute(MeshAttributes.Position);

// A position has 3 floats per vertex. Thus, positions has length 3 * 4.
const positions = positionAttribute.createArray(vertexCount);