Integrate with Credit card Authentication

  <!-- jQuery -->
  <script type="text/javascript" src="https://code.jquery.com/jquery-1.12.4.min.js" ></script>
  <!-- iamport.payment.js -->
  <script type="text/javascript" src="https://cdn.iamport.kr/js/iamport.payment-1.1.8.js"></script>

  var IMP = window.IMP; // Can be skipped.
  IMP.init("imp00000000"); // Replace "imp00000000" with the issued "Merchant ID".

  // Call IMP.certification(param, callback)
  IMP.certification({ // param
    merchant_uid: "ORD20180131-0000011",
    m_redirect_url : "https://www.myservice.com/certifications/redirect", // Required if popup: false (default) in mobile environment
    popup : false // popup parameter is ignored in PC environment and always applied as true
  }, function (rsp) { // callback
    if (rsp.success) {
      ...,
      // Logic of successful authentication,
      ...
    } else {
      ...,
      // Logic on authentication failure,
      ...
    }
  });

  IMP.certification({
    /* ...code omitted here... */
  }, function (rsp) { // callback
    if (rsp.success) { // If the authentication succeeds
      // HTTP request using jQuery
      jQuery.ajax({
        url: "https://www.myservice.com/certifications", // Service web server
        method: "POST",
        headers: { "Content-Type": "application/json" },
        data: { imp_uid: rsp.imp_uid }
      });
    } else {
      alert("Authentication failed. Error: " +  rsp.error_msg);
    }
  });

GET {m_redirect_url}?imp_uid={}&merchant_uid={authenticating merchant_uid}&success={true or false}

  app.use(bodyParser.json());
  ...
  // The controller to handle POST request for "/certifications": callback style 
  app.post("/certifications", async (request, response) => {
    const { imp_uid } = request.body; // Extract imp_uid from request body
  })
  ...
  // The controller to handle GET request for "/certifications/redirect": redirection style
  app.get("/certifications/redirect", async (request, response) => {
    const { imp_uid } = request.query; // Extract imp_uid from request query
  })

  app.use(bodyParser.json());
  ...
  // The controller to handle POST request for "/certifications"
  app.post("/certifications", async (request, response) => {
    const { imp_uid } = request.body; // Extract imp_uid from request body
    try {
      // Acquire access token
      const getToken = await axios({
        url: "https://api.iamport.kr/users/getToken",
        method: "post", // POST method
        headers: { "Content-Type": "application/json" }, // "Content-Type": "application/json"
        data: {
          imp_key: "imp_apikey", // REST API Key
          imp_secret: "ekKoeW8RyKuT0zgaZsUtXXTLQ4AhPFW3ZGseDA6bkA5lamv9OqDMnxyeB9wqOsuO9W3Mx9YSJ4dTqJ3f" // REST API Secret
        }
      });
      const { access_token } = getToken.data.response; // Authentication token
      ...
      // Query authentication information with imp_uid
      const getCertifications = await axios({
        url: \`https://api.iamport.kr/certifications/\${imp_uid}\`, // Pass imp_uid
        method: "get", // GET method
        headers: { "Authorization": access_token } // Append the authentication token to Authorization header
      });
      const certificationsInfo = getCertifications.data.response; // Retrieved authentication information
      ...
    } catch(e) {
      console.error(e);
    }
  });

  // The controller to handle POST request for "/certifications"
  app.post("/certifications", async (request, response) => {
    const { imp_uid } = request.body; // Extract imp_uid from request body
    try {
      // Acquire access token
      /* ...code omitted here... */
      // Query authentication information with imp_uid
      /* ...code omitted here... */
      const certificationsInfo = getCertifications.data.response; // Retrieved authentication information
            // unique_key: Unique identifier for a person, unique_in_site: Unique identifier for a person for each site
      const { unique_key, unique_in_site, name, gender, birth } = certificationsInfo;
      ...
      // Age limit logic
      if (new Date(birth).getFullYear() <= 1999) {
        // Age satisfied
      } else {
        // Age not satisfied
      }
      ...
      // Logic to limit one account for one person
      // Query unique_key from the database and check if the user has already signed up
      Users.find({ certificationKey: unique_key })
      .then((user) => {
        if (!user) {
          // New user
        } else {
          // User already signed up
        }
      });
    } catch(e) {
      console.error(e);
    }
  });