1 /*
  2     This sample code is provided by Annsa Ltd. for information only.
  3 */
  4 
  5 // Simple helper to return the "exMaxLen" attribute for
  6 // the specified field.  Using "getAttribute" won't work
  7 // with Firefox.
  8 function GetMaxLength(targetField)
  9 {
 10     return targetField.exMaxLen;
 11 }
 12 
 13 //
 14 // Limit the text input in the specified field.
 15 //
 16 function LimitInput(targetField, sourceEvent)
 17 {
 18     var isPermittedKeystroke;
 19     var enteredKeystroke;
 20     var maximumFieldLength;
 21     var currentFieldLength;
 22     var inputAllowed = true;
 23     var selectionLength = parseInt(GetSelectionLength(targetField));
 24     
 25     if ( GetMaxLength(targetField) != null )
 26     {
 27         // Get the current and maximum field length
 28         currentFieldLength = parseInt(targetField.value.length);
 29         maximumFieldLength = parseInt(GetMaxLength(targetField));
 30 
 31         // Allow non-printing, arrow and delete keys
 32         enteredKeystroke = window.event ? sourceEvent.keyCode : sourceEvent.which;
 33         isPermittedKeystroke = ((enteredKeystroke < 32)                                
 34                               ||(enteredKeystroke >= 33 && enteredKeystroke <= 40)    
 35                               ||(enteredKeystroke == 46))                            
 36 
 37         // Decide whether the keystroke is allowed to proceed
 38         if ( !isPermittedKeystroke )
 39         {
 40             if ( ( currentFieldLength - selectionLength ) >= maximumFieldLength ) 
 41             {
 42                 inputAllowed = false;
 43             }
 44         }
 45         
 46         // Force a trim of the textarea contents if necessary
 47         if ( currentFieldLength > maximumFieldLength )
 48         {
 49             targetField.value = targetField.value.substring(0, maximumFieldLength)
 50         }
 51     }   
 52     
 53     sourceEvent.returnValue = inputAllowed;
 54     return (inputAllowed);
 55 }
 56 
 57 //
 58 // Limit the text input in the specified field.
 59 //
 60 function LimitPaste(targetField, sourceEvent)
 61 {
 62     var clipboardText;
 63     var resultantLength;
 64     var maximumFieldLength;
 65     var currentFieldLength;
 66     var pasteAllowed = true;
 67     var selectionLength = GetSelectionLength(targetField);
 68 
 69     if ( GetMaxLength(targetField) != null )
 70     {
 71         // Get the current and maximum field length
 72         currentFieldLength = parseInt(targetField.value.length);
 73         maximumFieldLength = parseInt(GetMaxLength(targetField));
 74 
 75         clipboardText = window.clipboardData.getData("Text");
 76         resultantLength = currentFieldLength + clipboardText.length - selectionLength;
 77         if ( resultantLength > maximumFieldLength)
 78         {
 79             pasteAllowed = false;
 80         }    
 81     }    
 82     
 83     sourceEvent.returnValue = pasteAllowed;
 84     return (pasteAllowed);
 85 }
 86 
 87 //
 88 // Returns the number of selected characters in 
 89 // the specified element
 90 //
 91 function GetSelectionLength(targetField)
 92 {
 93     if ( targetField.selectionStart == undefined )
 94     {
 95         return document.selection.createRange().text.length;
 96     }
 97     else
 98     {
 99         return (targetField.selectionEnd - targetField.selectionStart);
100     }
101 }