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I have a textbox with multilines. I am restricting the max length using java script. My problem is, when I enter the values using keyboard it's validating my max length but when I copy a text and paste it the same is accepting the values more than the given max length. How can I restrict the max length when I copy and paste the content to the textbox?

Posted 24-Nov-10 23:03pm

MathewPV

Updated 24-Nov-10 23:07pm

JF2015

v2

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3 solutions

Solution 1

You can check the paste on the keyup. If the keycode = 86, check the length.

<HTML><head></head><body>
<form name="myForm">
Text: <input type="text" name="myText"
onKeyUp = "fncKeyLength(this);">
</form>
<script>
function fncKeyLength(text){
if (window.event.ctrlKey){
if (window.event.keyCode == 86) {
   alert("<br />The string is this long: " + text.length);

}
}}
</script></body></HTML>

Posted 24-Nov-10 23:06pm

Sebastien T.

Updated 24-Nov-10 23:11pm

v2

Comments

MathewPV 25-Nov-10 5:15am

sorry to say u i am new with web application i dont have much idea about java script i have inserted the following code but still its accepting paste in text box..
var key;
if(window.event)
{
key = window.event.keyCode; //IE
}
else
{
key = e.which; //firefox
}
if(key==86)

{
event.returnValue = false ;
}

Sandeep Mewara 25-Nov-10 5:18am

Well, 2 things:
1. 86 is a keycode of 'V' so, this would be executed every time you press key capital V
2. for small 'v', this will not get executed.

Though, your suggestion could be made for a normal scenario with handling both 'V' & 'v'

Sebastien T. 25-Nov-10 5:21am

Sandeep, it's true, thanks and you can test if "CTRL" is pressed. The correct test is:
if (e.ctrlKey && (e.keyCode == 118 || e.keyCode == 86))

MathewPV, because when keyup it is call, the textbox is normally already fill. If you want you can clear the textbox, (document.myform.Textbox1.value= "") or cut the text (document.myform.Textbox1.value= document.myform.Textbox1.value.substr(0, MAXLENGTH)

Ankur^\m/ 25-Nov-10 5:33am

There is still a problem with this code. A user can right click on the textbox and select paste.
I guess adding onpaste="return false;" would solve the issue.

MathewPV 25-Nov-10 5:35am

e.ctrlKey is giving me a runtime java script error e is undefined

MathewPV 25-Nov-10 5:37am

Ankur, the thing is want to use paste function after the maxlength is achieved then it should not paste the rest of the content

Ankur^\m/ 25-Nov-10 5:47am

Replace 'e' by 'event'.

Ankur^\m/ 25-Nov-10 5:49am

Okay, In that case, instead of returning false in onpaste event, write the same check you did in the above function inside it.

Dalek Dave 26-Nov-10 3:51am

Good Answer.

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Sebastien T. · Accepted Answer · 2010-11-25T00:00:00

Ok, Check with this code.

XML

<html>
  <head>
  </head>
  <body>
        <form id="myForm">
          <asp:textbox runat="server" id="TextBox1" maxlength="40" onpaste="fncCheckLength()">

          function fncCheckLength()
          {
              var textBox = document.myForm.TextBox1;
              if(textBox.value.length > MaxLength)
              {
                 alert("Text too long");
                 textBox.value = "";
              }
          }
  </body>
</html>

For the keyboard check, the correct code is (but the Ankur remark is true for right click):

XML

<html>
  <head>
  </head>
  <body>
        <form>
          Text: <input type="text" name="myText"
          onKeyUp = "fncKeyLength();">
          </form>
          <script>
          function fncKeyLength()
          {
            var key;
            var IsCtrl = false;
            if (window.event)
            {
              key = window.event.keyCode; //IE
              IsCtrl = window.event.ctrlKey;
            }
            else
            {
              key = e.which; //firefox
              IsCtrl =  e.ctrlKey;
            }
            if( IsCtrl && (key == 118 || key == 86 ) )
            {
               fncCheckLength();
            }
          }
          function fncCheckLength()
          {
              var textBox = document.myForm.TextBox1;
              if(textBox.value.length > MaxLength)
              {
                 alert("Text too long");
                 textBox.value = "";
              }
          }
  </body>
</html>

Toniyo Jackson · Accepted Answer · 2010-11-24T23:34:00

Solution 3

Add onpaste="return false;" in TextBox,

<asp:textbox runat="server" id="txtRef" maxlength="40" onpaste="return false;">

Posted 24-Nov-10 23:34pm

Toniyo Jackson

Updated 24-Nov-10 23:36pm

v2

Comments

Toniyo Jackson 25-Nov-10 5:37am

If its working fine accept the answer.

MathewPV 25-Nov-10 5:40am

Toni Jack, What you have given is correct i want to paste the content till the max length is achieved moreover my textbox mode is multiline