eolas/zk/Practical_walkthrough_Lambda_creation_within_AWS.md

---
tags: [AWS, aws-lambda, node-js]
---

# Practical walkthrough of creating a Lambda function via the AWS Management Console

## Basic set-up

First we name the function and accept the defaults:

![](/img/lambda_func_one.png)

This presents us with the function dashboard - a graphical representation of the
Lambda showing [triggers]() as an input and destination as an output:

![](/img/lambda-func-two.png)

Beneath this we have a code editor with the handler function with a basic
boilerplate:

![](/img/lambda-func-three.png)

## Adding a trigger

Next we need to add a [trigger](Lambda_triggers.md) that
execute the handler.

We will do this using [AWS API Gateway](AWS_API_Gateway.md). We
select "Add trigger" from the dashboard view and input basic settings:

![](/img/api-gateway-trigger.png)

Now we see this step displayed in the dashboard:

![](/img/lambda-overview.png)

With the endpoint and other settings displayed:

![](/img/trigger-info.png)

If we go to the endpoint URL
(`https://4kjqwbvd7g.execute-api.us-east-1.amazonaws.com/default/myFirstFunction`),
we will see the output: `Hello from Lambda`.

## Handling parameters

We can make the example more realistic by expanding the handler to accept query
parameters. We do this by accessing the value `queryStringParameters` on the
`event` object:

```js
exports.handler = async (event) => {
  const name = event.queryStringParameters && event.queryStringParameters.name;

  let message = "Hello Lambda";

  if (name !== null) {
    message = `Hello ${name}`;
  }

  const response {
    statusCode: 200,
    body: JSON.stringify(message)

  }
};
```

If we now access
`https://4kjqwbvd7g.execute-api.us-east-1.amazonaws.com/default/myFirstFunction?name=Thomas`

We get `Hello Thomas` as output.

For a more advanced API with multiple endpoints and parameters, it's easiest to
use Postman:

![](/img/postman-lambda.png)