node js read stream, write to a file and calculate hash

In the JavaScript file, write a program to perform a GET request on the route https://coderbyte.com/api/ challenges/json/age-counting which contains a data key and the value is a string which contains items in the format: key STRING, age INTEGER. Your goal is to count how many items exist that have an age equal to 32. Then you should create a write stream to a file called output.txt and the contents should be the key values (from the json) each on a separate line in the order they appeared in the json file (the file should end with a newline character on its own line). Finally, then output the SHA1 hash of the file.

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Example Input

["data":"key=IAfpK, age=32,

key WNVdi, age=64, key=jp9zt,

To complete your request, I'll provide a Node.js script that:

1. Makes a GET request to the specified API URL.

2. Parses the response to count how many items have an age of 32.

3. Writes the keys of all items to a file called output.txt, each on a new line.

4. Calculates and prints the SHA1 hash of the file contents.

Here's the complete Node.js script to achieve this:

const https = require('https');

const fs = require('fs');

const crypto = require('crypto');

// Function to fetch data from the API

function fetchData(callback) {

    const url = 'https://coderbyte.com/api/challenges/json/age-counting';

    https.get(url, (res) => {

        let data = '';

        res.on('data', (chunk) => {

            data += chunk;

        });

        res.on('end', () => {

            callback(data);

        });

    }).on('error', (err) => {

        console.error('Error fetching data: ', err);

    });

}

// Function to process data and write to file

function processData(data) {

    const result = JSON.parse(data);

    const items = result.data.split(', ');

    const outputStream = fs.createWriteStream('output.txt');

    let age32Count = 0;

    items.forEach((item) => {

        const [keyPart, agePart] = item.split(', age=');

        if (agePart && parseInt(agePart) === 32) {

            age32Count++;

        }

        const key = keyPart.split('=')[1];

        outputStream.write(`${key}\n`);

    });

    outputStream.end('\n');

    console.log(`Number of people aged 32: ${age32Count}`);

    outputStream.on('finish', () => calculateHash('output.txt'));

}

// Function to calculate SHA1 hash of the file

function calculateHash(filename) {

    const hash = crypto.createHash('sha1');

    const stream = fs.createReadStream(filename);

    stream.on('data', (data) => {

        hash.update(data);

    });

    stream.on('end', () => {

        const fileHash = hash.digest('hex');

        console.log(`SHA1 Hash of the file: ${fileHash}`);

    });

}

// Main function to run the process

function main() {

    fetchData(processData);

}

main();

Breakdown:

• **fetchData**: This function fetches data from the provided API endpoint.

• **processData**: This function processes the data to find keys, counts ages equal to 32, and writes the keys to output.txt.

• **calculateHash**: This function calculates the SHA1 hash of the output file.

• **main**: Orchestrates the entire process.

Ensure you have Node.js installed on your system to run this script. Save the script in a file and run it using the command node <filename.js>.