Determines the probability of a hash collision occuring and compares it to the probability of being killed by a shark or a meteor

hashcollision.js

#!/usr/bin/env node

/* https://preshing.com/20110504/hash-collision-probabilities/
 *
 * Question: "Given k randomly generated values, where each value is a
 * non-negative integer less than N, what is the probability that at least two
 * of them are equal?"
 *
 * In other words, what's the probability of a hash collision?
 *
 *                   -k(k - 1)
 * Answer: p = 1 - e^---------
 *                      2N
 *
 */

const _k = process.argv[2];
const k = eval(_k);
console.log(`k = ${_k} = ${k.toPrecision(3)} (number of hashes)`)
const _N = process.argv[3];
const N = eval(_N);
console.log(`N = ${_N} = ${N.toPrecision(3)} (hash size + 1)`);

console.log(); // newline

const p = 1 - Math.exp( (-k*(k - 1)) / ( 2*N ));

let probHuman = p.toPrecision(3);

const relativeShark = p / (1 / (300 * 10**6));
const relativeSharkHuman = relativeShark.toPrecision(3);

const relativeMeteor = p / (1 / (182 * 10**9));
const relativeMeteorHuman = relativeMeteor.toPrecision(3);

console.log(`The probability of a collision is: ${probHuman}`)
console.log(`That's ${relativeSharkHuman} the probability of dying in a shark attack.`);
console.log(`That's ${relativeMeteorHuman} the probability of your house getting hit by a meteor.`);

Example usage:
./hashcollision.js 10**6 2**(8*5)

For the probability of a hash collision with 10^6 hashes of 5 bytes each.