n8n/docs/nodes.md

Nodes

Function and Function Item Node

These are the most powerful nodes in n8n. With these, almost everything can be done if you know how to write JavaScript code. Both nodes work very similarly. They simply give you access to the incoming data and you can manipulate it.

Difference between both nodes

The difference is that the code of the Function-Node does get executed only once and it receives the full items (JSON and binary data) as an array and expects as return value again an array of items. The items returned can be totally different from the incoming ones. So is it not just possible to remove and edit existing items it is also possible to add or return totally new ones.

The code of the Function Item-Node on the other does get executed once for every item. It receives as input one item at a time and also just the JSON data. As a return value, it again expects the JSON data of one single item. That makes it possible to very easily add, remove and edit JSON properties of items but it is not possible to add new or remove existing items. Accessing and changing binary data is only possible via the methods getBinaryData and setBinaryData.

Both nodes support promises. So instead of returning the item or items directly, it is also possible to return a promise which resolves accordingly.

Function-Node

Variable: items

It contains all the items the node received as input.

Information about how the data is structured can be found on the page Data Structure

The data can be accessed and manipulated like this:

// Sets the JSON data property "myFileName" of the first item to the name of the
// file which is set in the binary property "image" of the same item.
items[0].json.myFileName = items[0].binary.image.fileName;

return items;

This example creates 10 dummy items with the ids 0 to 9:

const newItems = [];

for (let i=0;i<10;i++) {
  newItems.push({
    json: {
      id: i
    }
  });
}

return newItems;

Method: $item(index)

With $item it is possible to access the data of parent nodes. That can be the item data but also the parameters. It expects as input an index of the item the data should be returned for. This is needed because for each item the data returned can be different. This is probably obvious for the item data itself but maybe less for data like parameters. The reason why it is also needed there is that they may contain an expression. Expressions get always executed of the context for an item. If that would not be the case, for example, the Email Send-Node not would be able to send multiple emails at once to different people. Instead, the same person would receive multiple emails.

The index is 0 based. So $item(0) will return the first item, $item(1) the second one, ...

Example:

// Returns the value of the JSON data property "myNumber" of Node "Set" (first item)
const myNumber = $item(0).$node["Set"].data["myNumber"];
// Like above but data of the 6th item
const myNumber = $item(5).$node["Set"].data["myNumber"];

// Returns the value of the parameter "channel" of Node "Slack".
// If it contains an expression the value will be resolved with the
// data of the first item.
const channel = $item(0).$node["Slack"].parameter["channel"];
// Like above but resolved with the value of the 10th item.
const channel = $item(9).$node["Slack"].parameter["channel"];

Variable: $node

Works exactly like $item with the difference that it will always return the data of the first item.

const myNumber = $node["Set"].data['myNumber'];

const channel = $node["Slack"].parameter["channel"];

Method: getWorkflowStaticData(type)

Gives access to the static workflow data. It is possible to save data directly with the workflow. This data should, however, be very small. A common use case is to for example to save a timestamp of the last item that got processed from an RSS-Feed or database. It will always return an object. Properties can then read, deleted or set on that object. When the workflow execution did succeed n8n will check automatically if data changed and will save it if necessary.

There are two types of static data. The "global" and the "node" one. Global static data is the same in the whole workflow. And every node in the workflow can access it. The node static data , however, is different for every node and only the node which did set it can retrieve it again.

Example:

// Get the global workflow static data
const staticData = getWorkflowStaticData('global');
// Get the static data of the node
const staticData = getWorkflowStaticData('node');

// Access its data
const lastExecution = staticData.lastExecution;

// Update its data
staticData.lastExecution = new Date().getTime();

// Delete data
delete staticData.lastExecution;

It is important to know that static data can not be read and written when testing via the UI. The data will there always be empty and changes will not be persisted. Only when a workflow is active and it gets called by a Trigger or Webhook will the static data be saved.

Function Item-Node

Variable: item

It contains the "json" data of the currently processed item.

The data can be accessed and manipulated like this:

// Uses the data of an already existing key to create a new additional one
item.newIncrementedCounter = item.existingCounter + 1;
return item;

Method: getBinaryData()

Returns all the binary data (all keys) of the item which gets currently processed.

Method: setBinaryData(binaryData)

Sets all the binary data (all keys) of the item which gets currently processed.

Method: getWorkflowStaticData(type)

As described above for Function-Node.