> ## Documentation Index
> Fetch the complete documentation index at: https://docs.callivox.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Working with data
> Reshape lists inside a flow: map fields, filter rows, group and aggregate, deduplicate, sort, build arrays, convert JSON — and run a JavaScript snippet when nothing else fits.
Most flows start by fetching a list — rows from a sheet, records from a CRM, items from an API — and
the shape you get is rarely the shape you want. The **Data** section of the palette reshapes it
before it reaches whatever comes next.
Every Data block takes a list in and produces **Result** (the new list) plus **Count**, so they chain
end to end. A list can be a previous step's output, JSON text, or a single object.
## The blocks
Keep only the fields you name, under the names you want. The biggest lever on payload size.
Keep only the items matching a condition, with an optional second condition.
Collapse many rows into one item per group — count them, total them, merge their values.
Remove repeats, keeping the first of each.
Order a list by a field, ascending or descending.
Take the first N items, optionally after skipping some.
Create a list from scratch, or append to one you already have.
Turn JSON text into a list you can map, filter and group.
Turn a list back into JSON text for a response or message body.
A short script, for anything the blocks above cannot express.
Field names are matched **without regard to capitalisation**, and a name with dots in it reaches
inside nested values — `customer.city` reads the `city` inside `customer`.
## Map Items
Give it a **Field mapping**: a JSON object of the name you want on the left, the field it comes from
on the right.
```json theme={null}
{ "name": "Doctor Name", "department": "Department", "languages": "Languages" }
```
Everything not listed is dropped. Turn on **Keep unmapped fields** to keep the rest as well, in which
case a mapping simply renames.
## Filter Items
Pick a **Field**, a **Condition** and a **Value**. Available conditions: equals, does not equal,
contains, does not contain, starts with, ends with, greater than, greater than or equal, less than,
less than or equal, is empty, is not empty, is one of, is not one of. The last two take a
comma-separated list.
Add a **Second field** to test two things at once, combined with **AND** (both must match) or **OR**
(either may match).
Comparisons like *greater than* compare **numbers as numbers** when both sides look numeric, so
`10` is correctly greater than `9`. You do not have to declare a column type.
## Group & Aggregate
This is the block for turning a repeated export into one row per thing. A schedule with one row per
doctor per day becomes one row per doctor.
Set **Group by** to the field (or comma-separated fields) that identify a group, then list what each
group should contain in **Aggregations**:
```json theme={null}
[
{ "name": "department", "op": "first", "field": "Department" },
{ "name": "locations", "op": "join_distinct", "field": "Location", "separator": ", " },
{ "name": "visits", "op": "count" }
]
```
Each entry needs a **name** (the output field) and an **op**. Every op except `count` needs a
**field**.
| Op | Result |
| ----------------------------- | ----------------------------------------------------------------- |
| `count` / `count_distinct` | How many items, or how many different values |
| `first` / `last` | The first or last value in the group |
| `sum` / `avg` / `min` / `max` | Numeric totals and extremes |
| `join` / `join_distinct` | The values joined into one string, all or only the different ones |
| `list` / `list_distinct` | The values as a list |
**Include group fields** carries the group-by fields onto each result item. Leave it on unless you
have a reason not to.
**When a field varies inside a group, `first` throws the rest away.** A doctor who works at three
clinics has three different Locations in the group; `first` keeps one and silently loses two.
Use `join_distinct` (or `list_distinct`) for any field that legitimately differs within a group.
The same applies to **Unique Items** — it keeps one whole item and discards the others.
If you leave **Aggregations** empty *and* turn **Include group fields** off, there is nothing to
put in each group. The step will tell you rather than quietly returning empty items.
### Filter before you group
Rows that should not count must be removed *before* grouping. In a staff schedule, a day someone is
off is still a row, and it still carries a location — group without filtering and you will credit
people with places they never work.
`Time Start` **does not equal** `Off`
Group by `Doctor Name`, merging `Location` with `join_distinct`
Keep just the fields the answer needs
Compact, into the response body
## Run JavaScript
For a transform the other blocks cannot express. Prefer a regular block where one fits — those show
their inputs and outputs in the run history, while a script is opaque when something goes wrong.
```js theme={null}
var rows = getOutputFrom('sheets-find-1', 'Rows');
var out = [];
for (var r of rows) {
out.push({ name: r['Doctor Name'], dept: r.Department });
}
out;
```
* Read an earlier step with **`getOutputFrom('', '