three.js/src/core/InstancedBufferAttribute.js

import { BufferAttribute } from './BufferAttribute.js';

class InstancedBufferAttribute extends BufferAttribute {

	constructor( array, itemSize, normalized, meshPerAttribute = 1 ) {

		if ( typeof normalized === 'number' ) {

			meshPerAttribute = normalized;

			normalized = false;

			console.error( 'THREE.InstancedBufferAttribute: The constructor now expects normalized as the third argument.' );

		}

		super( array, itemSize, normalized );

		this.isInstancedBufferAttribute = true;

		this.meshPerAttribute = meshPerAttribute;

	}

	copy( source ) {

		super.copy( source );

		this.meshPerAttribute = source.meshPerAttribute;

		return this;

	}

	toJSON() {

		const data = super.toJSON();

		data.meshPerAttribute = this.meshPerAttribute;

		data.isInstancedBufferAttribute = true;

		return data;

	}

}

export { InstancedBufferAttribute };