lambda-typescript.md

Building Lambda functions with TypeScript

You can use the Node.js runtime to run TypeScript code in AWS Lambda. Because Node.js doesn't run TypeScript code natively, you must first transpile your TypeScript code into JavaScript. Then, use the JavaScript files to deploy your function code to Lambda. Your code runs in an environment that includes the AWS SDK for JavaScript, with credentials from an AWS Identity and Access Management (IAM) role that you manage.

Setting up a TypeScript development environment

Use a local integrated development environment (IDE), text editor, or AWS Cloud9 to write your TypeScript function code. You can’t create TypeScript code on the Lambda console.

To transpile your TypeScript code, set up a compiler such as esbuild or Microsoft's TypeScript compiler (tsc) , which is bundled with the TypeScript distribution. You can use the AWS Serverless Application Model (AWS SAM) or the AWS Cloud Development Kit (CDK) to simplify building and deploying TypeScript code. Both tools use esbuild to transpile TypeScript code into JavaScript.

When using esbuild, consider the following:

• There are several TypeScript caveats.
• You must configure your TypeScript transpilation settings to match the Node.js runtime that you plan to use. For more information, see Target in the esbuild documentation. For an example of a tsconfig.json file that demonstrates how to target a specific Node.js version supported by Lambda, refer to the TypeScript GitHub repository.
• esbuild doesn’t perform type checks. To check types, use the tsc compiler. Run tsc -noEmit or add a "noEmit" parameter to your tsconfig.json file, as shown in the following example. This configures tsc to not emit JavaScript files. After checking types, use esbuild to convert the TypeScript files into JavaScript.

Example tsconfig.json

 {
  "compilerOptions": {
    "target": "es2020",
    "strict": true,
    "preserveConstEnums": true,
    "noEmit": true,
    "sourceMap": false,
    "module":"commonjs",
    "moduleResolution":"node",
    "esModuleInterop": true, 
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true, 
    "isolatedModules": true, 
  },
  "exclude": ["node_modules", "**/*.test.ts"]
}

Topics

• Setting up a TypeScript development environment
• AWS Lambda function handler in TypeScript
• Deploy transpiled TypeScript code in Lambda with .zip file archives
• Deploy transpiled TypeScript code in Lambda with container images
• AWS Lambda function errors in TypeScript

The following topics about the Node.js runtime are also relevant for TypeScript:

• AWS Lambda context object in Node.js
• AWS Lambda function logging in Node.js
• Instrumenting Node.js code in AWS Lambda