line-ending.js

const fs = require('fs');
const args = process.argv.slice(2);
const [filename] = args;

fs.readFile(filename, 'utf8', (err, data) => {
    if (err) {
        return console.log(err);
    }

    let r = 0;
    let n = 0;
    let rn = 0;
    let output = '';

    for (let i = 0; i < data.length; i++) {
        switch(data[i]) {
            case '\r':
                if (data[i + 1] === '\n') {
                    rn += 1;
                    i += 1;
                    output += '\x1b[41m\x1b[37m\\r\\n\x1b[0m \n';    
                } else {
                    r += 1;
                    output += '\x1b[41m\x1b[37m\\r\x1b[0m \n';    
                }
                break;
            case '\n':
                r += 1;
                output += '\x1b[41m\x1b[37m\\n\x1b[0m \n';
                break;
            default:
                output += data[i];
                break;
        }
    }

    console.log(output);    
    console.log('------------------------');    
    console.log('r:  ', r);    
    console.log('n:  ', n);    
    console.log('rn: ', rn);    
});