README.md

Lambda Function URLs with JavaScript

Key	Value
Services	Lambda
Integrations	AWS CLI, Terraform
Categories	Serverless; REST API

Introduction

A demo application illustrating how to create a JavaScript Lambda function with a function URL using LocalStack. Lambda function URLs provide a dedicated HTTP(S) endpoint for invoking a Lambda function directly. The sample also demonstrates deploying the same setup using Terraform.

Prerequisites

• A valid LocalStack for AWS license. Your license provides a LOCALSTACK_AUTH_TOKEN to activate LocalStack.
• Docker
• localstack CLI
• awslocal CLI
• Terraform (optional, for Terraform-based deployment)

Check prerequisites

make check

Installation

make install

Start LocalStack

export LOCALSTACK_AUTH_TOKEN=<your-auth-token>
make start

Run the application

Deploy the Lambda function and create a function URL:

awslocal lambda create-function \
    --function-name localstack-lamba-url-example \
    --runtime nodejs20.x \
    --zip-file fileb://function.zip \
    --handler index.handler \
    --role arn:aws:iam::000000000000:role/cool-stacklifter

awslocal lambda create-function-url-config \
    --function-name localstack-lamba-url-example \
    --auth-type NONE

You will receive an HTTP URL in the form http://abcdefgh.lambda-url.us-east-1.localhost.localstack.cloud:4566. Invoke the Lambda function via HTTP POST:

curl -X POST \
    'http://abcdefgh.lambda-url.us-east-1.localhost.localstack.cloud:4566/' \
    -H 'Content-Type: application/json' \
    -d '{"num1": "10", "num2": "10"}'

Expected output:

The product of 10 and 10 is 100

Using Terraform

You can automate the Lambda function and function URL creation using Terraform:

terraform init
terraform plan
terraform apply --auto-approve

Since we are using LocalStack, no actual AWS resources will be created. LocalStack creates ephemeral development resources that are automatically cleaned up when you stop LocalStack (localstack stop).

License

This code is available under the Apache 2.0 license.