sort-by-covered.js

const fs = require('fs');

fs.readFile('lcov.info', 'utf8', (err, data) => {
    const arr = data.split('\n');

    let file;

    const counts = [];

    arr.forEach((a) => {
        const [id, value] = a.split(':');

        if (id === 'SF') {
            file = value;
            return;
        }

        if (id === 'DA') {
            const [ln, count] = value.split(',');
            counts.push({
                file,
                ln,
                count: parseInt(count, 10),
            });
        }
    });

    counts.sort((a, b) => {
        if (a.count > b.count) {
            return -1;
        }

        if (a.count < b.count) {
            return 1;
        }

        return 0;
    });

    const strs = counts.map(c => `${c.file},${c.ln},${c.count}`)

    fs.writeFile('cov.txt', strs.join('\n'), 'utf8', () =>
        console.log('done')
    );
});