Tyk v2.2 Documentation Components

Javascript API


Embedded Javscript interpreters offer the bare bones of a scripting language, but not necessarily the functions that you would expect, especially with JavaScript, where objects such as XMLHttpRequest() are a given. However, those interfaces are actually provided by the browser / DOM that the script engine are executing in. In a similar vein, we have included a series of functions to the JSVM for convenience and give the interpreter more capability.

This list is regularly revised and any new suggestions should be made in our Github issue tracker.

below is the list of functions currently provided by Tyk.


Calling log("this message") will cause Tyk to log the string to Tyk’s default logger output in the form JSVM Log: this message as an INFO statement. This function is especially useful for debugging your scripts, it is recommended to put a log() call at the end of your middleware and event handler module definitions to indicate on load that they have been loaded successfully – see the example scripts supplied with Tyk for more.


This method is used to make an HTTP request, requests are encoded as JSON for deserialisation in the min binary and translation to a system HTTP call. The request object has the following structure:

newRequest = {
    "Method": "POST",
    "Body": JSON.stringify(event),
    "Headers": {},
    "Domain": "http://foo.com",
    "Resource": "/event/quotas",
    "FormData": {"field": "value"}

Tyk passes a simplified response back which looks like this:

type TykJSHttpResponse struct {
    Code int
    Body string
    Headers map[string][]string

The response is JSON string encoded, and so will need to be decoded again before it is usable:

usableResponse = JSON.parse(response);
log("Response code: " + usableResponse.Code);
log("Response body: " + usableResponse.Body);

This method does not execute asynchronously, so execution will block until a response is received.

TykGetKeyData(api_key, api_id)

Use this method to retrieve a session object for the key and the API provided:

// In an event handler, we can get the key idea from the event, and the API ID from the context variable.
var thisSession = JSON.parse(TykGetKeyData(event.EventMetaData.Key, context.APIID))
log("Expires: " + thisSession.expires)

TykSetKeyData(api_key, api_id)

Use this method to write data back into the Tyk session store:

// You can modify the object just like with the REST API
thisSession.expires = thisSession.expires + 1000;

// Use TykSetKeyData to set the key data back in the session store
TykSetKeyData(event.EventMetaData.Key, JSON.stringify(thisSession));

All of these methods are described in functional examples in the tyk middleware/ and event_handlers/ folders.

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