I believe you are looking for the focus event.

<div>
  <label for="txtEmail">Email:</label>
  <input type="text" name="email" id="txtEmail" onblur="validateForm()" onkeypress="clearErrMsg()">
  <label id="lblError" style="color:red"></label>
</div>

  function validateForm() {
    var x = document.getElementById("txtEmail").value;
    var atpos = x.indexOf("@");
    var dotpos = x.lastIndexOf(".");
    if (atpos < 1 || dotpos < atpos + 2 || dotpos + 2 >= x.length) {
      document.getElementById("lblError").innerHTML = "Enter valid email Address";
    } else {
      document.getElementById("lblError").innerHTML = "";
    }
  }

  function clearErrMsg() {
    document.getElementById("lblError").innerHTML = "";
  }

Can i make my validate error be hidden while someone is typing in the field? (not focusing, only while typing more letters onto the input).

i currently have this code:

 <div>
  Email:
  <input type="text" name="email" id="txtEmail" onblur="validateForm()">
  <label id="lblError" style="color:red"></label>
  </div>

and this javascript:

function validateForm() {
     var x = document.getElementById("txtEmail").value;
     var atpos = x.indexOf("@");
     var dotpos = x.lastIndexOf(".");
     if (atpos < 1 || dotpos < atpos + 2 || dotpos + 2 >= x.length) {


         document.getElementById("lblError").innerHTML = "Enter valid email Address";
     }
     else {
         document.getElementById("lblError").innerHTML = "";
     }
 }

What this does is validate my e-mail input when input field loses focus.
However i would love for it to hide error when someone focuses again and write more letters.
Exactly like this site: https://www.cosstores.com/en_dkk/login

Is this possible with jquery or javacript?