Want response in JSONP format instead of JSON in nodejs using aws lambda and api gateway

Question

Want response in JSONP format instead of JSON in nodejs using aws lambda and api gateway. my lambda code is:

var axios = require("axios");

exports.handler = async (event) => {
  return new Promise((resolve, reject) => {
    var data = JSON.stringify({
      username: event.username,
      password: event.password,
    });
    var config = {
      method: "post",
      url: "http://demo.example.net/v2/api/login",
      headers: {
        "Content-type": "application/json",
      },
      data: data,
    };
    axios(config)
      .then(function (response) {
        const res = {
          statusCode: 200,
          body: "callbackParam([" + JSON.stringify(response.data) + "])",
        };
        resolve(res.body);
      })
      .catch(function (error) {
        const err = {
          statusCode: 401,
          body: error,
        };
        reject(err.body);
      });
  });
};

getting Response like:

"callbackParam([  {"token":"<token>","expiration": "2022-04-28T08:00:25Z"}])"

can anyone help me what i need to implement extra stuff to convert this response string to jsonp?

my expected response is callbackParam([{}])

Answer 1

I imagine you just need to respond with the appropriate content-type and body for a JavaScript resource.

You're also falling prey to the explicit promise construction anti-pattern so best avoid that too

exports.handler = async ({ username, password }) => {
  const { data } = await axios.post("http://demo.example.net/v2/api/login", {
    username,
    password,
  });

  return {
    statusCode: 200,
    headers: {
      "content-type": "application/javascript",
    },
    body: `callbackParam(${JSON.stringify([data])})`,
  };
};