Creating CRM Field Mask / Format

Yet another feature i would like to see MS provide out of the box. Quite simple to implement.
Call the Mask function providing the field id and mask (# acts as a placeholder) and you're done.
The end user only has to fill in the numbers e.g. 97356568987

function OnCrmPageLoad() 
{ 
Mask( "telephone2" , "+(###)-(#)###-###" ); 
Mask( "gi_visa" , "####-####-####-####" ); 
Mask( "gi_scid" , "#-########-#" ); 
}


function Mask( fieldId , mask ) 
{ 
field = document.getElementById(fieldId); 
field.mask = mask.split(""); 
field.regex = new RegExp(escapeRegEx(mask.replace(/#/gi,"").split("")),"gi"); 
field.title += " " + mask; 
field.attachEvent( "onchange" , MaskOnFieldChange ); 
}

function escapeRegEx( chars ) 
{ 
var regChars = "+_)(*^$[]-?{}"; //Add all regexp chars id needed 
var regExprs = ""; 
var run2Index = chars.length - 1;

for( var i = 0 ; i < run2Index ; i++ ) Concat( chars[i] , "|" );


Concat(chars[run2Index]); 


function Concat( c , d ){ 
regExprs += (( regChars.indexOf(c) != -1 )? "\\":"" ) + c + d; 
}

return regExprs; 
}


function MaskOnFieldChange() 
{ 
var field = event.srcElement; 
if( field.DataValue == null ) return; 

var arrDataValue = field.DataValue.replace(field.regex,"").split(""); 
var arrResult = [];

for(var i=0 , j=0 ; i < field.mask.length ;i++) 
arrResult[i] = (field.mask[i] != "#")?field.mask[i]:arrDataValue[j++];

field.DataValue = arrResult.join(""); 
}

OnCrmPageLoad();