Keyboard restriction textbox with options and ñ

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Introduction

This is a single way to implement a character restriction in a page. Using this Javascript we can to restrict the input characters in a specific way for each control textbox.

Javascript Code

The code is simple, a getkeycode(event) returns the javascript keycode or event.which, depends on the browser. 

 function getKeyCode(e)
{
 if (window.event)
    return window.event.keyCode;
 else if (e)
    return e.which;
 else
    return null;
}

And a keyRestrict(event, validcharacters_string) returns a true or false if the key pressed is a valid character or not.

function keyRestrict(e, validchars) {
 var key='', keychar='';
 key = getKeyCode(e);
 if (key == null) return true;
 keychar = String.fromCharCode(key);
 keychar = keychar.toLowerCase();
 validchars = validchars.toLowerCase();
 if (validchars.indexOf(keychar) != -1)
  return true;
 if ( key==null || key==0 || key==8 || key==9 || key==13 || key==27 )
  return true;
 return false;
}

Implementation

To use this is simple, just put a function call in the onkeypress event of the textbox

Numeric sample:

<input type="text" name="textfield" onKeyPress="return keyRestrict(event,'1234567890')">

Alfa (not alfanumeric just alfa in this case accepts a SPACE) 

<input type="text" name="textfield" onKeyPress="return keyRestrict(event,'abcdefghijklmnopqrstuvwxyz ')">

Ñ support (spanish keyboards for example).

Here a sample with the Ñ support. because if you type the 'ñ' in the string the script fail in the moment you press the ñ char.

to have Ñ suport we need to put the next code:

<input type="text" name="textfield" onKeyPress="return keyRestrict(event,'abcdefghijklmnopqrstuvwxyz '+String.fromCharCode(241))">

this is a simple script, but the Ñ support is usefull to me, and i wabt to share the solution