Why Is My n8n Expression Returning [object Object] Instead of the Expected Value?

The data structure isn’t at fault here. The expression

  return [{json:{test: $evaluateExpression($node["FileMaker Data API"].json["response"]["dataInfo"])}}]

returns an object for test. When an object is coerced to a string (for example, when it’s displayed in the result view), you’ll see "[object Object]". In your second example you’re extracting a specific property (database) which is a string ("Vitamines"), so it shows as expected.

If your intention is to inspect the entire dataInfo object as a string, you can stringify it:

JAVASCRIPTCopied
return [{
  json: {
    test: JSON.stringify($evaluateExpression($node["FileMaker Data API"].json["response"]["dataInfo"]))
  }
}]

This will return a JSON string of the object so you can see its full content. Otherwise, if you need to work with the object properties, simply access them directly as done with the "database" property.

For more details on how n8n handles JSON data between nodes, please refer to the n8n documentation on the data structure.

The issue you're seeing is not a bug in n8n but rather how JavaScript converts objects to strings. When you evaluate

JAVASCRIPTCopied
$node["FileMaker Data API"].json["response"]["dataInfo"]

you’re getting an object, so when it’s coerced into a string for output it becomes "[object Object]". In contrast, accessing a property like

JAVASCRIPTCopied
$node["FileMaker Data API"].json["response"]["dataInfo"]["database"]

returns a string value ("Vitamines") and displays correctly.

If you want to output the full object as a proper JSON string, you could use JSON.stringify. For example:

JAVASCRIPTCopied
return [{json: { test: JSON.stringify($evaluateExpression($node["FileMaker Data API"].json["response"]["dataInfo"])) }}]

This way, the object is serialized and you can see its content in your output.