Hacker-rank diagonal difference.js

'use strict';

const fs = require('fs');

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});

process.stdin.on('end', function() {
    inputString = inputString.replace(/\s*$/, '')
        .split('\n')
        .map(str => str.replace(/\s*$/, ''));

    main();
});

function readLine() {
    return inputString[currentLine++];
}

// Complete the diagonalDifference function below.
function diagonalDifference(arr) {
    let n = arr.length;
    let diag1 = 0;
      let  diag2 = 0;

    for (let i = 0; i < n; i++) {
        for (let j = 0; j < n; j++) {
            { i === j && (diag1 += arr[i][j]) }
            { (i + j === n - 1) && (diag2 += arr[i][j]) }
        }
    }

    return Math.abs(diag1 - diag2)

}

function main() {
    const ws = fs.createWriteStream(process.env.OUTPUT_PATH);

    const n = parseInt(readLine(), 10);

    let arr = Array(n);

    for (let i = 0; i < n; i++) {
        arr[i] = readLine().split(' ').map(arrTemp => parseInt(arrTemp, 10));
    }

    const result = diagonalDifference(arr);

    ws.write(result + '\n');

    ws.end();
}