Untitled

<form>

  <input type="password" name="pass1" id="pass1">

  <input type="password" name="pass2" id="pass2">

</form>

<div id="check"></div>

window.onload=init;

function init() {

  document.querySelector("#pass2").onkeyup = function() {

    var pass1 = document.querySelector("#pass1").value;

    var pass2 = document.querySelector("#pass2").value;

    if (pass1 != pass2) {

      document.querySelector("#check").innerHTML = "fout";

    } else {

      document.querySelector("#check").innerHTML = "goed";

    }

  }

}