javascript textbox call event when value changes

Question

I have a textbox, and whenever the value of the box changes, I want to check and see if 20 digits have been entered.

I thought that I would use the onChange event, but this seems to be interpreted as the onBlur event on IE.

So then I thought I would use onKeyDown, but the problem comes in if the user wants to paste a value into the field, then the function never gets called.

There are no other form boxes so I can't rely on onBlur or expect that they will change focus ever.

How do I do this?

I just want to evaluate the value of the textbox everytime the value of the textbox changes.

<input type="text" onKeyDown="myfunction()">

Answer 1

use onKeryPress event

 <input type="text" onKeyDown="CountText(this,200)" onpaste="return false;"> 

    function CountText(field, maxlimit) 
    {
       if (field.value.length < maxlimit) // if too long...trim it!
        {
            return true;
        }
        else
          return false;
    }

check my full article on : http://www.codeproject.com/KB/validation/MyTextBox.aspx

Answer 2

An effective way is to use a combination of onkeydown and onpaste, which will work in IE, Firefox, Chrome and Safari. Opera is the odd one out here because it doesn't support onpaste so you may have to fall back to onchange for Opera or use the DOMAttrModified mutation event, see example below.

Internet Explorer also supports onpropertychange, which will fire every time a property changes on an element -- including value. I have read that DOMAttrModified is supported by Opera and Safari (not sure about Firefox), so you could use that in combination with IE's onpropertychange (untested):

if ("implementation" in document &&
                   document.implementation.hasFeature('MutationEvents','2.0'))
    myInput.addEventListener("DOMAttrModified", valueChanged, false);    
else if ("onpropertychange" in myInput)
    myInput.onpropertychange = valueChanged;

function valueChanged (evt)
{
    var attr;
    evt = evt || window.event;
    attr = evt.attrName || evt.propertyName;

    if (attr == "value")
        validate();
}