Functions

Functions are used to mutate webhook payloads (event data) before they are dispatched based on a passed user-defined Javascript function.

Convoy uses goja to provide a JavaScript runtime environment in Go, providing full ECMAScript 5.1 support (including regex and strict mode). Most of the ECMAScript 6 spec is implemented, but this is a work in progress. To enhance the runtime, console support from goja_nodejs was also added.

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Importing Modules

require support also exists but is currently disabled.

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Caveats

Certain constraints exist while using functions:

• Multiple functions can be written in the file, but only the transform function is invoked.
• Only the first argument is used in the transform function and that is the payload data.
• The transform function must return a value.

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Use cases

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Subscriptions

Functions can be configured when creating or updating a subscription. This is currently only possible in incoming projects. The function is used to mutate ingested event payloads from webhook providers before sending them to the destination endpoints.

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Sources

Functions can be configured when creating a message broker source in an outgoing project. The function is used to mutate ingested event payloads from the message broker before sending them to the destination endpoints.

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Example

{
	"blockchain": "optimism",
	"chainId": "10",
	"connectedAddresses": [
		{
			"address": "0xca3a901d1bd21be11b88e4e9d534fb48d35dde48",
			"blockchain": "ethereum",
			"chainId": "1",
			"timestamp": "2023-05-18T16:07: 22Z"
		}
	],
	"profileImageContentValue": {
		"image": {
			"original": "10/caster/9613/profile_image/original_image.jpg"
		}
	},
	"userAssociatedAddresses": [
		"0x4e4814f10e341882438264c85ba8f02ef8f8a592",
		"0xca3a901d1bd21be11b88e4e9d534fb48d35dde41",
		"0x3628bbc094720495489f6ac726ef7233c3d9587e"
	],
	"userId": "9613"
}

function transform(payload) {
    return {
        "event_type": "chain.connected",
        "data": {
            "addresses": payload.connectedAddresses[0].address,
            "created_at": new Date(payload.connectedAddresses[0].timestamp).getTime(),
            "user_id": payload.userId
        }
    };
}

{
	"data": {
		"addresses": "0xca3a901d1bd21be11b88e4e9d534fb48d35dde48",
		"created_at": 1684426042000,
		"user_id": "9613"
	},
	"event_type": "chain.connected"
}