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134 lines
3.1 KiB
Markdown
134 lines
3.1 KiB
Markdown
# Mapping in the UI
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Data mapping means referencing data from previous nodes. It doesn't include changing (transforming) data, just referencing it.
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You can map data in the following ways:
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* Using the expressions editor.
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* By dragging and dropping data from the **INPUT** table or JSON into parameters. This generates the expression for you.
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## How to drag and drop data
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1. Run your workflow to load data.
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2. Open the node where you need to map data.
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3. You can map in both table and JSON view:
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* In table view: click and hold a table heading to map top level data, or a field in the table to map nested data.
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* In JSON view: click and hold an attribute.
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4. Drag the item into the parameter field where you want to use the data.
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### Understand nested data
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Given the following data:
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```js
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[
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{
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"name": "First item",
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"nested": {
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"example-number-field": 1,
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"example-string-field": "apples"
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}
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},
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{
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"name": "Second item",
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"nested": {
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"example-number-field": 2,
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"example-string-field": "oranges"
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}
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}
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]
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```
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n8n displays it in table form like this:
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## Map data in the expressions editor
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These examples show how to access linked items in the expressions editor. Refer to [expressions](/code-examples/expressions/) for more information on expressions, including built in variables and methods.
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### Access the linked item in a previous node's output
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When you use this, n8n works back up the item linking chain, to find the parent item in the given node.
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```js
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// Returns the linked item
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{{$("<node-name>").item}}
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```
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As a longer example, consider a scenario where a node earlier in the workflow has the following output data:
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```json
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[
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{
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"id": "23423532",
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"name": "Jay Gatsby",
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},
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{
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"id": "23423533",
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"name": "José Arcadio Buendía",
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},
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{
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"id": "23423534",
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"name": "Max Sendak",
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},
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{
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"id": "23423535",
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"name": "Zaphod Beeblebrox",
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},
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{
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"id": "23423536",
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"name": "Edmund Pevensie",
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}
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]
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```
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To extract the name, use the following expression:
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```js
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{{$("<node-name>").item.json.name}}
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```
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### Access the linked item in the current node's input
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In this case, the item linking is within the node: find the input item that the node links to an output item.
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```js
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// Returns the linked item
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{{$input.item}}
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```
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As a longer example, consider a scenario where the current node has the following input data:
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```json
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[
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{
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"id": "23423532",
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"name": "Jay Gatsby",
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},
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{
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"id": "23423533",
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"name": "José Arcadio Buendía",
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},
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{
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"id": "23423534",
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"name": "Max Sendak",
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},
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{
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"id": "23423535",
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"name": "Zaphod Beeblebrox",
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},
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{
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"id": "23423536",
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"name": "Edmund Pevensie",
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}
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]
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```
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To extract the name, you'd normally use drag-and-drop [Data mapping](/data/data-mapping/), but you could also write the following expression:
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```js
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{{$input.item.json.name}}
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```
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