Transformers

Use a transformer when a query returns data in a shape that needs to be simplified or reshaped before it reaches your app.

Transformers are written in JavaScript.

What transformers receive

Transformers can access:

• data - the query results
• params - the bindings passed to the query

Create a transformer

1. Create a datasource and query
2. Open the transformer editor for the query
3. Write JavaScript to reshape the response
4. Send the query to test the output
5. Save the query

Return shape

A transformer must return an array.

If you return a single object, Budibase wraps it as one row.

If you return an array of values, Budibase treats each value as a row.

Example

Use a transformer to count breweries by state.

const counts = {}

for (const brewery of data) {
  const state = brewery.state
  counts[state] = (counts[state] || 0) + 1
}

return Object.entries(counts).map(([state, count]) => ({
  state,
  count,
}))

You can also add derived fields, such as a flag URL, before returning the final rows.

Common uses

• Flatten nested API responses
• Count or group records
• Add derived fields
• Convert API data into a table-friendly shape

Notes

• Keep the query working first, then refine the transformer
• Use params for binding values passed into the query
• Re-test the query after changing the transformer