API Gateway Response Builder

This module will help you build a valid API Gateway response from your lambda function.

Install

npm i @kdcio/api-gw-resp

Usage

import response from '@kdcio/api-gw-resp';

export const listMovies = (event) => {
  const body = {
    movies: [
      { name: 'Lord of the Rings' },
      { name: 'Forest Gump' },
      { name: 'Breaveheart' },
    ],
  };
  return response.OK({ body });
};

The function above will return

{
  "statusCode": 200,
  "isBase64Encoded": false,
  "headers": {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Credentials": true,
    "Access-Control-Allow-Headers": "*"
  },
  "body": "{\"movies\":[{\"name\":\"Lord of the Rings\"},{\"name\":\"Forest Gump\"},{\"name\":\"Breaveheart\"}]}"
}

API

Successful responses

Method	Code	Description
OK	200	Request has succeeded and the message body contains the requested information.
CREATED	201	Request has succeeded and a new resource has been created. The message body may contain information about the new resource.
NO_CONTENT	204	Request has succeeded but there is no content to be returned.

Options

Option	Type	Required	Default	Description
body	object, string or null	☑️	null	object will be converted into JSON string and will have a Content-Type of application/json in the header. string will have a Content-Type of text/plain in the header.
cors	bool	☑️	true	If true, will add cors in header
origin	string	☑️	*	Set specific origin
headers	object	☑️	{}	Specify additional headers

Examples:

response.OK({ body: { name: 'John Doe' } });
response.CREATED({ body: { id: 1 } });
response.NO_CONTENT();

Redirect responses

Method	Code	Description
REDIRECT	301 or 302	The URI of the requested resource has moved. The new URI can be found in the Location header.

Options

Option	Type	Required	Default	Description
permanent	bool	☑️	none	If true, status code will be 301. Otherwise it will be 302.
location	bool	☑️	none	The new url where the resource has been moved.
headers	object	☑️	{}	Specify additional headers

Examples:

response.REDIRECT({
  permanent: true,
  location: 'https://www.google.com',
});

Client Error responses

Method	Code	Description
BAD_REQUEST	400	The server could not understand the request due to invalid syntax or missing parameters.
UNAUTHORIZED	401	The client must authenticate itself to get the requested response.
FORBIDDEN	403	The client is not allowed to access the requested resource. Unlike 401, the client's identity is known to the server.
NOT_FOUND	404	The server can not find the requested resource.
CONFLICT	409	This response is sent when a request conflicts with the current state of the server. Usually duplicate of data.

Options

Option	Type	Required	Default	Description
error	string	☑️	Status code name	Error name
message	string	✅	none	Error message

Examples:

response.BAD_REQUEST({ message: 'Missing username' });
response.UNAUTHORIZED({
  message: 'You need to login to access this resource.',
});
response.FORBIDDEN({ message: 'You are not allowed to access this resource.' });
response.NOT_FOUND({ message: 'Resource not found.' });
response.CONFLICT({ message: 'Duplicate username.' });

Server Error responses

Method	Code	Description
SERVER_ERROR	500	The server has encountered a situation it doesn't know how to handle.

Options

Option	Type	Required	Default	Description
error	string	☑️	Internal Server Error	Error name
message	string	✅	none	Error message

Examples:

response.SERVER_ERROR({ message: 'Internal server error.' });

Auto Detect Error responses

Method	Description
ERROR	This will auto detect which error code to send based on the message.

Options

Option	Type	Required	Default	Description
message	string	✅	none	Error message

Error Messages

Error Response	Regex matcher
BAD_REQUEST	/missing|invalid/i
UNAUTHORIZED	/unauthorized/i
FORBIDDEN	/forbidden|not allowed/i
NOT_FOUND	/not found/i
CONFLICT	/conflict|duplicate/i

Examples:

try {
  throw new Error('Missing username');
} catch (e) {
  // This will return status code 400 (BAD_REQUEST)
  return response.ERROR({ message: e.message });
}

More Examples

import parser from '@kdcio/api-gw-req';
import response from '@kdcio/api-gw-resp';
import db from './db';

export const movie = async (event) => {
  const request = parser(event);
  let body = null;

  if (event.method === 'GET') {
    try {
      const movies = db.listMovies();
      return response.OK({ body: { movies } });
    } catch (e) {
      return response.BAD_REQUEST({ message: e.message });
    }
  } else if (event.method === 'POST') {
    try {
      const id = await db.insertMove(request.body);
      return response.OK({ body: { id } });
    } catch (e) {
      return response.BAD_REQUEST({ message: e.message });
    }
  } else if (event.method === 'PUT') {
    try {
      await db.updateMove(request.body);
      return response.NO_CONTENT();
    } catch (e) {
      return response.CONFLICT({ message: e.message });
    }
  }

  return response.BAD_REQUEST({
    message: 'Invalid method',
  });
};

Using ERROR method:

import parser from '@kdcio/api-gw-req';
import response from '@kdcio/api-gw-resp';
import db from './db';

export const movie = async (event) => {
  const request = parser(event);
  let body = null;

  try {
    if (event.method === 'GET') {
      const movies = db.listMovies();
      return response.OK({ body: { movies } });
    } else if (event.method === 'POST') {
      const id = await db.insertMove(request.body);
      return response.OK({ body: { id } });
    } else if (event.method === 'PUT') {
      await db.updateMove(request.body);
      return response.NO_CONTENT();
    } else {
      throw new Error('Invalid method');
    }
  } catch (e) {
    // Will determine the correct status code based on the error message
    return response.ERROR({ message: e.message });
  }
};

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You can also:

See also

@kdcio/api-gw-req

License

MIT