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AWS Lambda Function Handler

In this article, we will discuss the AWS Lambda function handler.

Purpose

The Lambda function handler is the method in your function code that processes the event.

Async Handlers

These are the methods to perform an asynchronous task. Consider the following code: -

exports.handler = async (event) => {
    // TODO implement
    const response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Lambda!'),
    };
    return response;
};

Here is the output: -

Picture showing the output of async handler in lambda function

Click to Enlarge

Non-Async Handlers

These are the methods to perform the synchronous task. Consider the following code: -

exports.handler = (event,context,callback) => {
    // TODO implement
    const response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Lambda!'),
    };
    callback(null, response);
};

Here is the output: -

Picture showing the output of non-async handler in lambda function

Click to Enlarge

Arguments In The Handler Method

There are three arguments in the handler method: -

Event object → This object contains the information about the invoker
Context object → This object contains information about the invocation, function, and execution environment
Callback → This argument is used to send a response from the non-async handlers

Posted By -	Karan Gupta

Posted On -	Tuesday, January 31, 2023

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