Score and sort a list of hex strings by most entropy

rng-sort.js

/**
 * Sort a list of hexadecimal strings
 * by the most unique bytes per line (ie. most entropy).
 * Useful when searching a list for RNG values, such as cryptographic keys.
 */

const fs = require('fs');
const [, , file] = process.argv;
const content = fs.readFileSync(file);
const lines = content.toString().split(/\n/g);

const score = s => {
    let idx = {};
    let score = s.length/2;
    for (let i=0; i<s.length; i+=2) {
        const hex = s.substr(i,2);
        if (null != idx[hex]) score--;
        idx[hex] = true;
    }
    return score;
};
const stats = [];
for (const line of lines) {
    if ('' == line) continue;
    stats.push({ line: line, score: score(line) });
}
stats.sort((a, b) => {
    if (a.score < b.score) return +1
    else if (a.score > b.score) return -1;
    else return 0;
});
for (const line of stats) {
    // console.log(line);
    console.log(`${line.line}  ${line.score}`);
}