Solution - nodejs design pattterns - 3.1

index.mjs

import { EventEmitter } from "events";
import { readFile } from "fs";

class FindRegex extends EventEmitter {
        constructor(regex) {
                super();
                this.regex = regex;
                this.files = [];
        }

        addFile(file) {
                this.files.push(file);
                return this;
        }

        find() {
                process.nextTick(() => this.emit("findstart", this.files));

                for (const file of this.files) {
                        readFile(file, "utf8", (err, content) => {
                                if (err) {
                                        return this.emit("error", err);
                                }

                                this.emit("fileread", file);

                                const match = content.match(this.regex);

                                if (match) {
                                        match.forEach((el) => this.emit("found", file, el));
                                }
                        });
                }
                return this;
        }
}

const find = new FindRegex(/test1/);

find
        .addFile("file1.txt")
        .addFile("file2.txt")
        .find()
        .on("findstart", () => {
                console.log("find start");
        })
        .on("found", (file, match) => console.log(`Matched ${match} in file ${file}`))
        .on("fileread", () => console.log("file read "));