Validar RUT Chileno

validar_rut.js

function validarRut (rut) {
			if (rut.length == 0 || rut.length < 8) { 
				return false; 
			}

			rut = rut.replace('-','').replace(/\./g,'');
			var sum = 0,
				chars = "1234567890kK",
				counter = 0;
			for (var i = 0; i < rut.length; i++) {
				u = rut.substring(i, i + 1);
				
				if (chars.indexOf(u) != -1) {
					counter++;
				}
			}

			if (counter == 0) {
				return false;
			}
			
			var rut = rut.substring(0, rut.length - 1);
			var drut = rut.substring(rut.length - 1);
			var digit = '0';
			var mul = 2;
			
			for (i = rut.length - 1 ; i >= 0; i--) {
				sum = sum + rut.charAt(i) * mul;
				mul = (mul == 7) ? 2 : mul + 1;
			}
			res = sum % 11;
			if (res == 1 || res == 0) {
				digit = (res == 1 ) ? 'k' : '0';
			}
			else {
				digit = (11 - res) + "";
			}

			return digit == drut.toLowerCase();
		}