API Gateway HTTP Response for AWS Lambda

A small library that generates API Gateway HTTP responses for Lambda proxy integration. It can be used with AWS CloudFormation and AWS SAM.

Usage

This package exports a function that accepts four params and returns an object.

Function Params

Function accepts following four params:

• Response body (optional) - A string or an object that should be returned as a HTTP response from the API Gateway. Default value is an empty string.

• Status code (optional) - A number that represents HTTP status code. Default values are:

  • 204, if response body is an empty string.
  • 200, if response body is a string or an object.
  • 400, if response body is an instance of JavaScript Error.

• Headers (optional) - An object with headers that will be passed as response headers. Default value is:

  {
      "Access-Control-Allow-Headers": "Content-Type,Authorization,X-Amz-Date,X-Api-Key,X-Amz-Security-Token",
  	"Access-Control-Allow-Methods": "OPTIONS,POST,GET,PUT,DELETE",
  	"Access-Control-Allow-Origin": "*",
  	"Access-Control-Max-Age": "86400"
  }

• isBase64Encoded (optional) - true or false to enable or disable base64 encoding. Default value is false.

Output

The output of this function is an object in a valid Lambda function proxy integration format, described here. For example, a valud output for httpResponse('hello world') would be the following object:

{
    "isBase64Encoded": false,
    "statusCode": 200,
    "body": "hello world",
    "headers": {
   		"Access-Control-Allow-Headers": "Content-Type,Authorization,X-Amz-Date,X-Api-Key,X-Amz-Security-Token",
		"Access-Control-Allow-Methods": "OPTIONS,POST,GET,PUT,DELETE",
		"Access-Control-Allow-Origin": "*",
		"Access-Control-Max-Age": "86400"
	}
}

Example usage

A common usage would be inside an AWS Lambda function, similar to this:

'use strict'

const httpResponse = require('api-gateway-http-response')
const parseApiEvent = require('./parse-event') // A function that parses an event
const businessLogic = require('./business-logic') // A function that handles a logic for your Lambda function

async function lambda(event) {
  const request = parseApiEvent(event)
  try {
    const body = await businessLogic(request)
    return httpResponse(body)
  } catch(err) {
    return httpResponse(err)
  }
}

exports.handler = lambda

CORS support

By default, this function will return headers that supports CORS from any origin. Supported HTTP methods are: OPTIONS, POST, GET, PUT and DELETE.

Motivation

I wrote similar thing many times, packing it into a small independent package is easier that searching through other projects.

License

MIT -- see LICENSE