const useCapture = true; // capture, bubbling: false

button = document.getElementsByTagName('button')[0];
button.addEventListener('click',hashcash,false);
button.addEventListener('submit',hashcash,false);
console.log(button)

function hashcash(ev) {
  console.log('hashcash.ev: %o',ev);
  let algo = document.getElementsByName('algo')[0].value;
  let data = document.getElementsByName('data')[0].value;
  let nonce = document.getElementsByName('nonce')[0].value || '12131054600136590020';
  let dif = document.getElementsByName('dif')[0].value;
  let url = api_url + `hashcash?a=${algo}&b=${data}&n=${nonce}&d=${dif}`
  document.getElementById('pow').innerText = 'no-proof';
  let promised = fetch(url).
  then(resp => resp.json()).
  then(obj => {
    console.log('pow.hashcash.obj:',obj);
    document.getElementsByName('hashcash')[0].innerText = '0x'+obj.hash;
    document.getElementsId('pow').innerText = obj.pow;

  }).
  catch(console.error);
}

let url = api_url + 'config';

let promised = fetch(url).
  then(resp => resp.json()).
  then(obj => {
    console.log('pow.obj.config:',obj.config);
    let dif = obj.config.difficulty
    console.log('pow.dif:',dif);
    let elem = document.getElementById('dif');
    elem.innerText = dif;
    //let buf = elem.innerHTML; buf = buf.replace(':dif',dif); elem.innerHTML = buf;
        elem = document.getElementsByName('dif')[0];
    elem.value = dif;
    return obj.config
  }).
  catch(console.error)