问使用nodejs读取非常大的数据文件？面试问题

EN

const readline = require('node:readline');
const fs = require('node:fs');

// sample input data per line
// 3830591998918656: { "id": "2208ef95-355c-53a6-96bc-206a4831f2fe", "data": "Tu" }
// 548113328635904: { "id": "d5887987-bf5d-5813-b524-722ffff11882", "data": "Vubiteh hone na dabupkof tetnut." }
// 4322085113430016: { "id": "8f5330b9-0279-5a67-aee3-d6acf221a53a", "data": "Losu nihpe upaveitpse teblujnis." }
// 6348702421614592: { "id": "1fef0dbc-c75b-5959-835f-80e5f15b6da1", "data": "Riliv kaliku laiza zen daze ." }

const scoreRegex = /^\s*(\d+):\s*/;

function parseLine(line) {
    // ok to skip empty lines
    if (line.trim() === "") return null;

    const result = {};
    // parse leading digits
    const scoreMatch = line.match(scoreRegex);
    if (!scoreMatch) throw new Error("Missing score at beginning of line");
    result.score = BigInt(scoreMatch[1], 10);
    const remainingLine = line.slice(scoreMatch[0].length);
    result.info = JSON.parse(remainingLine);
    if (typeof result.info.id !== "string" || result.info.id === "") {
        throw new Error("Missing valid id value");
    }
    return result;
}

// input and output files
const fileInput = "input.txt";
const fileOutput = "output.txt";

const howManyHighest = 2;
const highestScores = [];

function getLowest() {
    return highestScores[highestScores.length - 1].score;
}

// do an insertion sort into the highestScores array
// highest score record first
// maintain length at no more than howManyHighest
function insertHighest(val) {
    let inserted = false;
    // for performance reasons, only search through the highestScores
    // list if this new score is higher than the lowest score we have in the list so far
    if (highestScores.length && val.score > getLowest()) {
        for (let [index, item] of highestScores.entries()) {
            if (val.score > item.score) {
                // insert it into this position in the array, pushing the others up
                highestScores.splice(index, 0, val);
                inserted = true;
                break;
            }
        }
    }
    if (inserted) {
        // trim overflow, if any
        if (highestScores.length > howManyHighest) {
            highestScores.pop();
        }
    } else {
        // didn't insert it, see if we aren't full yet
        if (highestScores.length < howManyHighest) {
            highestScores.push(val);
        }
    }
}

const rl = readline.createInterface({
    input: fs.createReadStream(fileInput),
    crlfDelay: Infinity
});

rl.on('error', err => {
    if (err.code === 'ENOENT') {
        process.exit(1);
    } else {
        console.log(err);
        // some sort of read error
        process.exit(2);
    }
}).on('line', line => {
    try {
        const data = parseLine(line);
        if (data) {
            insertHighest(data);
        }
    } catch (e) {
        console.log(e);
        console.log(`Invalid line: ${line}`);
        process.exit(2);
    }

}).on('close', () => {
    // generate array of highest scores
    const output = highestScores.map(item => item.info.id)
    console.log(output);
    fs.writeFile(fileOutput, JSON.stringify(output), err => {
        if (err) {
            console.log(err);
            // output write error
            process.exit(3);
        } else {
            // all done, successfully
            process.exit(0);
        }
    });
});