node/tools/eslint/lib/util/node-event-generator.js

/**
 * @fileoverview The event generator for AST nodes.
 * @author Toru Nagashima
 */

"use strict";

//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------

/**
 * The event generator for AST nodes.
 * This implements below interface.
 *
 * ```ts
 * interface EventGenerator {
 *     emitter: EventEmitter;
 *     enterNode(node: ASTNode): void;
 *     leaveNode(node: ASTNode): void;
 * }
 * ```
 */
class NodeEventGenerator {

    /**
     * @param {EventEmitter} emitter - An event emitter which is the destination of events.
     */
    constructor(emitter) {
        this.emitter = emitter;
    }

    /**
     * Emits an event of entering AST node.
     * @param {ASTNode} node - A node which was entered.
     * @returns {void}
     */
    enterNode(node) {
        this.emitter.emit(node.type, node);
    }

    /**
     * Emits an event of leaving AST node.
     * @param {ASTNode} node - A node which was left.
     * @returns {void}
     */
    leaveNode(node) {
        this.emitter.emit(`${node.type}:exit`, node);
    }
}

module.exports = NodeEventGenerator;