validation in javascript - remove the error msg on focus

Question

i'm not very well-versed with javascript, so please bear with me.

i've a form in which i validate the controls with javascript. the error is displayed when the fields are empty via a div, but when i focus and type something in the textbox, the div should go away. but the error div doesn't and even if i type something valid, it still displays the div.

i'd like to know where am i going wrong with this script:

<script type="text/javascript">
var err = document.getElementById("errmsg");

function checkInput(inPut) {

    if (inPut.getValue() == "") {
            err.setStyle('display', 'block');
            err.setTextValue("Field cannot be empty!");
            inPut.focus();
            return false;
    }
    else {
            return true;
    }

}


function checkTextBox(textBox)
{

    if (textBox.getValue() == "") {
          err.setStyle('display', 'block');
          err.setTextValue("Field cannot be empty!");
          textBox.focus();
         return false;
    }     
    else if (!checkValidity(textBox.getValue())) {
                 err.setStyle('display', 'block');
         err.setTextValue("Please enter a valid email address!");
         textBox.focus();
         return false;
    }
    else {
         return true;
    }
}

. . . 
<div id="errmsg" class="invalid" style="display:none;"></div> <br />

. . . 
<input type="text" tabindex="1" name="name" id="name" class="input_contact" onblur="checkInput(this);"/>  <br />

. . . 
<input type="text" tabindex="2" name="email" id="email" class="input_contact" onblur="checkTextBox(this);"/>  <br />

it's a form in facebook app but while the fbjs works, i assume there's a problem with my basic javascript.

Answer 1

try this

var err = document.getElementById("errmsg");

function checkInput(inPut) {

    if (inPut.getValue() == "") {
            err.setStyle('display', 'block');
            err.setTextValue("Field cannot be empty!");
            inPut.focus();
            return false;
    }
    else {
            err.setStyle('display', 'none');
            err.setTextValue("");
            return true;
    }

}


function checkTextBox(textBox)
{

    if (textBox.getValue() == "") {
          err.setStyle('display', 'block');
          err.setTextValue("Field cannot be empty!");
          textBox.focus();
         return false;
    }     
    else if (!checkValidity(textBox.getValue())) {
         err.setStyle('display', 'block');
         err.setTextValue("Please enter a valid email address!");
         textBox.focus();
         return false;
    }
    else {
         err.setStyle('display', 'none');
         err.setTextValue("");
         return true;
    }
}

Answer 2

To get the div to disappear when you first type something, instead of when the field is checked, you'll also need onchange and/or onfocus event handlers for the fields:

<input type="text" tabindex="1" name="name" id="name" class="input_contact"
    onblur="checkInput(this);"
    onfocus="err.setStyle('display', 'none');"
    onchange="err.setStyle('display', 'none');"
/>

They could also be set inside checkInput(), if you so desire.