Calculates shannon entropy in node.js

entropy.js

let raw = fs.readFileSync('./wannacrydump')
// console.log(raw)
let freqList = []

console.log(`Bytes: ${raw.length}`)

const getEntropy = (bytes) => {
    for (let i = 0; i < 255; i++) {
        let ctr = 0
        for (byte of bytes) {
            if (byte == i) {
                ctr++
            }
        }
        freqList.push(ctr / bytes.length)
    }
    let ent = 0.0
    for (const [ind, freq] of freqList.entries()) {
        if (freq > 0) {
            ent = ent + (freq * Math.log2(freq))
        }
    }
    ent = -ent
    console.log('Shannon entropy (min bits per byte-character):')
    console.log(ent)
    console.log('Min possible file size assuming max theoretical compression efficiency:')
    console.log(ent * raw.length)
}