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function nipValidator(el) {
	var nip = el.value;
	var nip_bez_kresek = nip.replace(/-/g,"");
	var reg = /^[0-9]{10}$/;
	
	if(reg.test(nip_bez_kresek) == false) {
		el.errors.push("Nieprawidłowy numer NIP.");
		return false;
	}
	else{
		var dig = (""+nip_bez_kresek).split("");
		var kontrola = (6*parseInt(dig[0]) + 5*parseInt(dig[1]) + 7*parseInt(dig[2]) + 2*parseInt(dig[3]) + 3*parseInt(dig[4]) + 4*parseInt(dig[5]) + 5*parseInt(dig[6]) + 6*parseInt(dig[7]) + 7*parseInt(dig[8]))%11;
		if(parseInt(dig[9])==kontrola) {
			return true;
		}
		else {
			el.errors.push("Nieprawidłowy numer NIP.");
			return false;
		}
	}
}