I need to change the class of the input based on text value. When the value is empty it should be default, when there is a value it should change the class to inputtext.

<style>
    .inputnotext{ background:#ddd; }
    .inputtext{ background:transparent } /* when their is text */
</style>

<form>
    <input class="inputnotext" type="text" name="firstname" /><br />
    <input class="inputnotext" type="text" name="lastname" />
</form> 

<script>
    /* script to write ??? */
</script>

I need to change the class of the input based on text value. When the value is empty it should be default, when there is a value it should change the class to inputtext.

<style>
    .inputnotext{ background:#ddd; }
    .inputtext{ background:transparent } /* when their is text */
</style>

<form>
    <input class="inputnotext" type="text" name="firstname" /><br />
    <input class="inputnotext" type="text" name="lastname" />
</form> 

<script>
    /* script to write ??? */
</script>

• javascript
• html

• 3 What have you tried so far? Stack Overflow is for help fixing errors and problems, not to write your code for you. – Rory McCrossan Commented Nov 29, 2011 at 10:25
• do you use jQuery or any other library? – Variant Commented Nov 29, 2011 at 10:26

3 Answers 3

This is a javascript which you can use:

var input = document.getElementsByTagName('input');

keyupHandler = function(input){
    if (input.value.length){
        input.setAttribute('class', 'inputnotext');
    }
    else {
        input.setAttribute('class', '');
    }
}

for (i=0; i<input.length; i++){
    input[i].onkeyup = function(){
        keyupHandler(this);
    }
    input[i].onchange = function(){
        keyupHandler(this);
    }
}

jsFiddle example

Up-to-date version (using event listener and classList):

var input = document.getElementsByTagName('input');

input.addEventListener('keyup', (e) => {
    e.target.classList.toggle("inputnotext", e.target.value );
});

jsFiddle example

Try the following code:

    <style>
         .inputnotext{ background:#ddd; } 
        .inputtext{ background:transparent } /* when their is text */ 
        </style>

        <form> 
        <input class="inputnotext" type="text" name="firstname" onblur="checkValue(this);"/><br /> 
        <input class="inputnotext" type="text" name="lastname" onblur="checkValue(this);"/> 
        </form> 

        <script> 
        function checkValue(c){
          var val = c.value;
    var id = c.id;
    if(val.length > 0){
    document.getElementById(id).className += "inputtext";
    }else{
document.getElementById(id).className += "inputnotext";

}
          } 
        </script>

Hope it helps you :-)

You could do something like this using jQuery:

$(document).ready($(input:text[name=firstname]).change(function() {
  var val = $(input:text[name=firstname]).val()
  if(val!="")
  {
     $(input:text[name=firstname]).removeClass("inputnotext").addClass("inputtext");
  }