read-first-line/dist/main.js

Read first line of the file. Works fine with LF and CRLF line endings.

"use strict";
const fs = require("fs");
function readFirstLine(filePath) {
    return new Promise((resolve, reject) => {
        const rs = fs.createReadStream(filePath, { encoding: "utf8" });
        let acc = "";
        let pos = 0;
        let index;
        rs.on("data", function (chunk) {
            index = chunk.indexOf("\r\n");
            if (index === -1) {
                index = chunk.indexOf("\n");
            }
            acc += chunk;
            index !== -1 ? rs.close() : (pos += chunk.length);
        })
            .on("close", function () {
            if (index !== -1) {
                return resolve(acc.slice(0, pos + index));
            }
            resolve(acc.slice(0, pos));
        })
            .on("error", function (err) {
            reject(err);
        });
    });
}
module.exports = readFirstLine;