three.js/examples/jsm/nodes/accessors/UVNode.js

import { TempNode } from '../core/TempNode.js';
import { NodeLib } from '../core/NodeLib.js';

function UVNode( index ) {

	TempNode.call( this, 'v2', { shared: false } );

	this.index = index || 0;

}

UVNode.prototype = Object.create( TempNode.prototype );
UVNode.prototype.constructor = UVNode;
UVNode.prototype.nodeType = 'UV';

UVNode.prototype.generate = function ( builder, output ) {

	builder.requires.uv[ this.index ] = true;

	var uvIndex = this.index > 0 ? this.index + 1 : '';
	var result = builder.isShader( 'vertex' ) ? 'uv' + uvIndex : 'vUv' + uvIndex;

	return builder.format( result, this.getType( builder ), output );

};

UVNode.prototype.copy = function ( source ) {

	TempNode.prototype.copy.call( this, source );

	this.index = source.index;

	return this;

};

UVNode.prototype.toJSON = function ( meta ) {

	var data = this.getJSONNode( meta );

	if ( ! data ) {

		data = this.createJSONNode( meta );

		data.index = this.index;

	}

	return data;

};

NodeLib.addKeyword( 'uv', function () {

	return new UVNode();

} );

NodeLib.addKeyword( 'uv2', function () {

	return new UVNode( 1 );

} );

export { UVNode };