// Module included in the following assemblies
//
// * serverless/functions/serverless-developing-nodejs-functions.adoc

:_mod-docs-content-type: REFERENCE
[id="serverless-nodejs-functions-context-objects_{context}"]
= Node.js context objects

Functions are invoked by providing a `context` object as the first parameter. This object provides access to the incoming HTTP request information.

.Example context object
[source,javascript]
----
function handle(context, data)
----

This information includes the HTTP request method, any query strings or headers sent with the request, the HTTP version, and the request body. Incoming requests that contain a `CloudEvent` attach the incoming instance of the CloudEvent to the context object so that it can be accessed by using `context.cloudevent`.

[id="serverless-nodejs-functions-context-objects-methods_{context}"]
== Context object methods

The `context` object has a single method, `cloudEventResponse()`, that accepts a data value and returns a CloudEvent.

In a Knative system, if a function deployed as a service is invoked by an event broker sending a CloudEvent, the broker examines the response. If the response is a CloudEvent, this event is handled by the broker.

.Example context object method
[source,javascript]
----
// Expects to receive a CloudEvent with customer data
function handle(context, customer) {
  // process the customer
  const processed = handle(customer);
  return context.cloudEventResponse(customer)
    .source('/handle')
    .type('fn.process.customer')
    .response();
}
----

[id="serverless-nodejs-functions-context-objects-cloudevent-data_{context}"]
== CloudEvent data

If the incoming request is a CloudEvent, any data associated with the CloudEvent is extracted from the event and provided as a second parameter. For example, if a CloudEvent is received that contains a JSON string in its data property that is similar to the following:

[source,json]
----
{
  "customerId": "0123456",
  "productId": "6543210"
}
----

When invoked, the second parameter to the function, after the `context` object, will be a JavaScript object that has `customerId` and `productId` properties.

.Example signature
[source,javascript]
----
function handle(context, data)
----

The `data` parameter in this example is a JavaScript object that contains the `customerId` and `productId` properties.