Create Lambda Function in node.js

Lambda Function In Node.js

AWS Lambda invokes your Lambda function via a handler object. A handler represents the name of your Lambda function (and serves as the entry point that AWS Lambda uses to execute your function code. For example:

exports.myHandler = function(event, context, callback) { ... function code callback(null, "some success message"); // or // callback("some error type"); }

• myHandler – This is the name of the function AWS Lambda invokes. Suppose you save this code as helloworld.js. Then, myHandler is the function that contains your Lambda function code and helloworld is the name of the file that represents your deployment package.
  AWS Lambda supports two invocation types:
  • RequestResponse, or synchronous execution: AWS Lambda returns the result of the function call to the client invoking the Lambda function. If the handler code of your Lambda function does not specify a return value, AWS Lambda will automatically return null for that value.
  • Event, or asynchronous execution: AWS Lambda will discard any results of the function call.
    
    
• context – AWS Lambda uses this parameter to provide details of your Lambda function's execution.
• callback (optional)

Example

Consider the following Node.js example code.

exports.myHandler = function(event, context, callback) { console.log("value1 = " + event.key1); console.log("value2 = " + event.key2); callback(null, "some success message"); // or // callback("some error type"); }

This example has one function, myHandler

In the function, the console.log() statements log some of the incoming event data to CloudWatch Logs. When the callback parameter is called, the Lambda function exits only after the event loop passed is empty.

If you want to use the async feature provided by the v8.10 runtime, consider the following code sample:

exports.myHandler = async function(event, context) { console.log("value1 = " + event.key1); console.log("value2 = " + event.key2); return "some success message”; // or // throw new Error(“some error type”); }

To upload and test this code as a Lambda function (console)

1. In the console, create a Lambda function using the following information:
   • Use the hello-world blueprint.
   • The sample uses nodejs6.10 as the runtime but you can also select nodejs8.10. The code samples provided will work for any version.
   For instructions to create a Lambda function using the console, see Create a Simple Lambda Function.
2. Replace the template code with the code provided in this section and create the function.
3. Test the Lambda function using the Sample event template called Hello World provided in the Lambda console.