AWS Lambda - Getting path parameters using Node.js - node.js

Question

In an AWS lambda written in Node.js, I want to extract the following part of a URL when I do a GET call through the API gateway:
/devices/{id} --> {id} will be replaced by a value, and that is the value I want!
I know that to get QueryStringParameters you just use
event.queryStringParameters.[parameter name]
But how will I do this for path parameters, like for {id} above.
Also is there a good place where I can comprehensively learn about writing lambdas for APIs in Node.js?

Answer 1

Short answer:
const { id } = event.pathParameters;
I recently released a short training video that demonstrates in detail how to create API Gateway REST APIs and integrate them with AWS Lambda (NodeJS). Please check it out here:
Serverless Architecture: AWS API Gateway & Lambda

Answer 2

I'm assuming you are using lambda proxy here i'm pasting the event object sample for lambda proxy.
{
"message": "Good day, John of Seattle. Happy Friday!",
"input": {
"resource": "/{proxy+}",
"path": "/Seattle",
"httpMethod": "POST",
"headers": {
"day": "Friday"
},
"queryStringParameters": {
"time": "morning"
},
"pathParameters": {
"proxy": "Seattle"
},
"stageVariables": null,
"requestContext": {
"path": "/{proxy+}",
"accountId": "123456789012",
"resourceId": "nl9h80",
"stage": "test-invoke-stage",
"requestId": "test-invoke-request",
"identity": {
"cognitoIdentityPoolId": null,
"accountId": "123456789012",
"cognitoIdentityId": null,
"caller": "AIDXXX...XXVJZG",
"apiKey": "test-invoke-api-key",
"sourceIp": "test-invoke-source-ip",
"accessKey": "ASIXXX...XXDQ5A",
"cognitoAuthenticationType": null,
"cognitoAuthenticationProvider": null,
"userArn": "arn:aws:iam::123456789012:user/kdeding",
"userAgent": "Apache-HttpClient/4.5.x (Java/1.8.0_131)",
"user": "AIDXXX...XXVJZG"
},
"resourcePath": "/{proxy+}",
"httpMethod": "POST",
"apiId": "r275xc9bmd"
},
"body": "{ \"callerName\": \"John\" }",
"isBase64Encoded": false
}
}
the path can be extracted from "path" key in event object, it can be accessed from event.path and after that you can use string manipulation function to further manipulate it.
I hope it helps !

Answer 3

Use brackets in the resource path, as image above. Then in node.js user the code below:
exports.handler = async function(event) {
let serviceId = event.pathParameters.id;
}

Answer 4

The solution is very similar to what you mentioned in the first place. Just use event.pathParameters instead of event.queryStringParameters.

Answer 5

Here I'm using /api/test/{id} as my resource path and using Lambda Proxy integration. I'm getting the following event when I hit https://www.dummyapi.com/dev/api/test/id-123456

Answer 6

This has taken me awhile to figure out on my own so hoping this helps someone. After defining the Path Parameter on the Resource in API Gateway.
AWS Guide including PathParameter Steps: https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-create-api-step-by-step.html
If using CloudFormation: https://aws.amazon.com/premiumsupport/knowledge-center/api-gateway-proxy-path-parameter-error/
My path /user/{userId}
My Path Parameter: userId
Then in my lambda function you can access the path via event.path which will have your parameters in object form: path: { userId: 9812 } }. Lots of documentation has it labeled as pathParameters but for whatever reason with this setup it doesn't come through that way.
export const getUser = async (event) => {
console.log(event);
const { userId } = event.path;
}
serverless.yaml
events:
- http:
path: user/{userId}
method: get
request:
parameters:
paths:
userId: true
integration: lambda