three.js/examples/jsm/renderers/nodes/core/FunctionNode.js

import CodeNode from './CodeNode.js';
import FunctionCallNode from './FunctionCallNode.js';

class FunctionNode extends CodeNode {

	constructor( code = '' ) {

		super( code );

		this.inputs = [];

		this.useKeywords = true;

	}

	getNodeType( builder ) {

		return this.getNodeFunction( builder ).type;

	}

	getInputs( builder ) {

		return this.getNodeFunction( builder ).inputs;

	}

	getNodeFunction( builder ) {

		const nodeData = builder.getDataFromNode( this );

		let nodeFunction = nodeData.nodeFunction;

		if ( nodeFunction === undefined ) {

			nodeFunction = builder.parser.parseFunction( this.code );

			nodeData.nodeFunction = nodeFunction;

		}

		return nodeFunction;

	}

	call( parameters = {} ) {

		return new FunctionCallNode( this, parameters );

	}

	generate( builder, output ) {

		super.generate( builder );

		const nodeFunction = this.getNodeFunction( builder );

		const name = nodeFunction.name;
		const type = nodeFunction.type;

		const nodeCode = builder.getCodeFromNode( this, type );

		if ( name !== '' ) {

			// use a custom property name

			nodeCode.name = name;

		}

		const propertyName = builder.getPropertyName( nodeCode );

		nodeCode.code = this.getNodeFunction( builder ).getCode( propertyName );

		if ( output === 'property' ) {

			return propertyName;

		} else {

			return builder.format( `${ propertyName }()`, type, output );

		}

	}

}

export default FunctionNode;