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TextBox only write String Character

By , 4 Aug 2007
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Introduction

In this article I will show how to make the script control TextBox have the following value: " Enter String Only " When the user clicks on the TextBox it becomes blank, and when the user deletes the written value from " Enter String Only " it re-requests an entry, and if the user tries to write a non-string character in the TextBox that character will not be written.

Using the Code

inputtext_onclick()

When the user deletes words from the entry " Enter String Only " fulltext_befor_new_char is set to "" or to the TextBox value that function fires when the user clicks on the TextBox.

function inputtext_onclick() 
{ 
// if the TextBox value = "Enter String Only" that mean
// the use not written any words yat so set the textbox
// value to "" and fulltext_befor_new_char Variable to "" 
if ((TextBox_Element.value == "Enter String Only")) 
{ 
TextBox_Element.value=""; 
fulltext_befor_new_char = ""; 
} 
Else 
// else mean mean the user written words befor as save it in
//fulltext_befor_new_char Variable 
fulltext_befor_new_char = TextBox_Element.value; 
}

inputtext_onblur()

This function is responsible for rewriting " Enter String Only " words if the user doesn't write any words that the function fires when the TextBox loses focus.

function inputtext_onblur() 
{ 
// if the textbox value = "" then the use laft the text box empty so
//set textbox value to "Enter String Only" agane 
if ((TextBox_Element.value == "")) 
TextBox_Element.value="Enter String Only"; 
}

inputtex_onkeydown(e)

function inputtex_onkeydown(e)
{ 
// cheak if the user use firefox
if (IsFireFox())
{
    // if firefox use e.which
    var key_code = e.which ;
}
else 
{
    // if not firefox use event.keyCode
    var key_code = event.keyCode ;
}
// cheak if the user press backspace key to delete writen character
// if not backspace then cheak 
if (key_code != 8)
{
    var ch = String.fromCharCode(key_code);
    var filter = /[a-zA-Z]/ ;
    if(!filter.test(ch))
    {
        //Cancel the Input
        if (IsFireFox())
        e.preventDefault(); 
        else
        event.returnValue = false ;
    }
}
} 
function inputtext_onkeypress() 
{ 
var fulltext = TextBox_Element.value; 
// if character legal then save textbox value in
//fulltext_befor_new_char Variable texbox value to 
if (Filter(fulltext)) 
{ 
fulltext_befor_new_char = TextBox_Element.value; 
} 
Else 
// if character illegal then set the texbox value to
//fulltext_befor_new_char ( old textbox value ) 
{ 
TextBox_Element.value = fulltext_befor_new_char; 
} 
}

function inputtex_onchange()

The function responsible for checking if the value is legal or illegal if the user pastes or drops the value:

function inputtex_onchange()
{
var inputtex_vlaue = TextBox_Element.value;
var filter = /^[a-zA-Z]+$/ ;
if(!filter.test(inputtex_vlaue))
    {
        TextBox_Element.value = "Enter String Only";
    }
}
function
add_Events_To_TextBox(TextBox_Name_Client)

The function responsible on adding (onkeydownonclickonbluronchange) events to the textbox in RunTime that the function fires after the document on page Load.

function add_Events_To_TextBox(TextBox_Name_Client) 
{ 

TextBox_Element = document.getElementById(TextBox_Name_Client);
TextBox_Element.onkeydown=function(event)
                    {
                        inputtex_onkeydown(event);
                    };
TextBox_Element.onclick=inputtext_onclick ;
TextBox_Element.onblur=inputtext_onblur;
TextBox_Element.onchange = inputtex_onchange;
}

In the ASPX file write at end of <form></form> element:

<script language="javascript" type="text/javascript" src="Unwrite_aspx.js" > 
</script> 
<script language="javascript" type="text/javascript" > 
add_Events_To_TextBox("<%=Unwrite_TestBox.ClientID%>"); 
</script>

Happy coding …

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

mohamed antar
Web Developer
Egypt Egypt
No Biography provided

Comments and Discussions

 
QuestionAnother Solution PinmemberMostafa Metwally2-Mar-13 9:31 
Under Event KeyPress
 
private void textbox_KeyPress(object sender, KeyPressEventArgs e)
        {
            e.Handled = !Char.IsLetter(e.KeyChar);
        }

Generalstring?! PinmemberAdam Tibi6-Aug-07 5:43 
GeneralRe: string?! Pinmembermohamed antar6-Aug-07 6:25 
GeneralMore simple solution PinmemberAlex.Shnaider29-Jul-07 3:53 
GeneralRe: More simple solution Pinmembermohamed antar29-Jul-07 23:07 
GeneralRe: More simple solution PinmemberLouisa Chen30-Jul-07 16:22 
GeneralRe: More simple solution PinmemberAlex.Shnaider30-Jul-07 19:19 
GeneralRe: More simple solution Pinmembermohamed antar30-Jul-07 20:06 
GeneralLittle Formatting is required PinmemberVasudevan Deepak Kumar28-Jul-07 21:50 
GeneralRe: Little Formatting is required Pinmembermohamed antar29-Jul-07 23:07 

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