How to get currency format while typing in text box from user end

i tried this for 10000000, Output is 1,0,0,0,0,000 But i need Output Like this 1,00,00,000

function ValidateAmount(txt) {
			var key;
			if (window.event)
				key = window.event.keyCode; // Chrome or IE only
			if (key == 32) {
				//alert(" White Space Not Allowed ");
				var str = document.getElementById(txt.id).value;
				str = str.replace(/\s/g, '');
				document.getElementById(txt.id).value = str;
			}

			str = document.getElementById(txt.id).value;
			
			str = str.toString();
			var lastThree = str.substring(str.length - 3);
			var otherNumbers = str.substring(0, str.length - 3);
			if (otherNumbers != '')
				lastThree = ',' + lastThree;
			var res = otherNumbers.replace(/\B(?=(\d{2})+(?!\d))/gi, ",") + lastThree; 
			document.getElementById(txt.id).value = res;
}