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 every time the value of the textbox changes.

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

Andy E · Accepted Answer · 2010-08-30 01:16:44Z

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();
}

Pranay Rana · Accepted Answer · 2010-05-13 19:12:14Z

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

answered May 13, 2010 at 19:12

Pranay Rana

177k37 gold badges244 silver badges266 bronze badges

1 Comment

Zenexer Over a year ago

keydown and keypress are not the same. Pick one. keyup would be the best if you want the majority of key events, but don't need to know when keys repeat (you'll just be notified when the key is finally released). If you need to recognize changed immediately, use keydown. keypress ignores non-printing keys, like backspace.

Bhanu Pratap · Accepted Answer · 2016-08-03 12:04:38Z

0

    <script>

function multy(val)
{
alert(val.value+"--"+val.id);
}

</script>
</head>
<body>
<input id="txtdemo" type="text" onchange="multy(this);"></br>
<input id="txtdemo" type="text" onchange="multy(this);">
</input>
</body>

Thanks... :)

answered Aug 3, 2016 at 12:04

Bhanu Pratap

1,76118 silver badges17 bronze badges

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