three.js/examples/jsm/renderers/common/Attributes.js

import DataMap from './DataMap.js';
import { AttributeType } from './Constants.js';
import { DynamicDrawUsage } from 'three';

class Attributes extends DataMap {

	constructor( backend ) {

		super();

		this.backend = backend;

	}

	delete( attribute ) {

		const attributeData = super.delete( attribute );

		if ( attributeData !== undefined ) {

			this.backend.destroyAttribute( attribute );

		}

	}

	update( attribute, type ) {

		const data = this.get( attribute );

		if ( data.version === undefined ) {

			if ( type === AttributeType.VERTEX ) {

				this.backend.createAttribute( attribute );

			} else if ( type === AttributeType.INDEX ) {

				this.backend.createIndexAttribute( attribute );

			} else if ( type === AttributeType.STORAGE ) {

				this.backend.createStorageAttribute( attribute );

			}

			data.version = this._getBufferAttribute( attribute ).version;

		} else {

			const bufferAttribute = this._getBufferAttribute( attribute );

			if ( data.version < bufferAttribute.version || bufferAttribute.usage === DynamicDrawUsage ) {

				this.backend.updateAttribute( attribute );

				data.version = bufferAttribute.version;

			}

		}

	}

	_getBufferAttribute( attribute ) {

		if ( attribute.isInterleavedBufferAttribute ) attribute = attribute.data;

		return attribute;

	}

}

export default Attributes;