stop the annoying captcha with hashcash

nocaptcha.js

const sha256 = require('hash.js').sha256

module.exports = {
  function pow(input, diff) {
    let candidate = 0;
    let nonce = 0;
    while(true) {
      nonce = Math.random()
      candidate = sha256().update(input + nonce.toString()).dig
est('hex')
      if(parseInt(candidate, 16) < diff) break
    }
    console.log('proof: ' + candidate)
    return nonce.toString()
  }

  function verify(input, diff, proof) {
    if(parseInt(sha256().update(input+proof).digest('hex'), 16)
 < diff) return true
    return false
  }
}
/* test
const diff = 22085588309729804119791218759286481447843548710945
2369765200775161577472
const proof = pow('this is my kung fu', diff)
console.log(verify('this is my kung fu', diff, proof))
*/