123.html

<!DOCTYPE html>
<html>
<head></head>
<body>

<input type="button" id="naverPayBtn" value="네이버페이 결제 버튼">
<script src="https://nsp.pay.naver.com/sdk/js/naverpay.min.js"></script>
<script>
    var oPay = Naver.Pay.create({
          "mode" : "production", // development or production
          "clientId": "u86j4ripEt8LRfPGzQ8" // clientId
    });

    //직접 만드신 네이버페이 결제버튼에 click Event를 할당하세요
    var elNaverPayBtn = document.getElementById("naverPayBtn");

    elNaverPayBtn.addEventListener("click", function() {
        oPay.open({
          "merchantUserKey": "1234",
          "merchantPayKey": "222",
          "productName": "312312",
          "totalPayAmount": "1000",
          "taxScopeAmount": "1000",
          "taxExScopeAmount": "0",
          "returnUrl": "사용자 결제 완료 후 결제 결과를 받을 URL"
        });
    });

</script>

</body>
</html>