---
title: Use reduce() to construct a JSON object
description: Learn how to send multiple points with http.post() by creating a JSON object with reduce().
url: https://docs.influxdata.com/flux/v0/process-data/construct-json-with-reduce/
estimated_tokens: 775
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/process-data/construct-json-with-reduce/
date: '2026-06-30T16:01:54-05:00'
lastmod: '2026-06-30T16:01:54-05:00'
---

Use the [`reduce()`](/flux/v0/stdlib/universe/reduce/) function to create a
JSON object to include as the body with `http.post()`.

1. Import both the [`array` package](/flux/v0/stdlib/array/) to query data
   and construct a table, and the [`http` package](/flux/v0/stdlib/http/) to
   transfer JSON over HTTP.

2. Use `array.from()` to query data and construct a table, or use another
   method to [query data with Flux](/influxdb/v2/query-data/flux/).

3. Use the `reduce()` function to construct a JSON object, and then use`yield()` to store the output of `reduce()`. This table looks like:

   |         field         |              tag               |
   |-----------------------|--------------------------------|
   |`example-field:["3"4"1`|`{example-tag-key:["bar"bar"bar`|

4. Use the [`map()`](/flux/v0/stdlib/universe/map/) function to combine the
   two columns into a JSON object, and then use a second `yield()` function to
   store this object as `final JSON`. This table looks like:

   |         field         |              tag               |                           final                           |
   |-----------------------|--------------------------------|-----------------------------------------------------------|
   |`example-field:["3"4"1`|`{example-tag-key:["bar"bar"bar`|`{example-tag-key:["bar"bar"bar] , example-field:["3"4"1]}`|

5. Use the `findRecord()` function to extract the value from the `final`column, the JSON.

6. Use `http.post()` to specify a URL to send the JSON to. This example uses[Post Test Server](https://ptsv2.com/) as the URL to send the JSON to and
   test the `http.post()` function.

```js
import "array"
import "http"

data = array.from(
        rows: [
            {_time: 2020-01-01T00:00:00Z, _field: "example-field", _value: 3, foo: "bar"},
            {_time: 2020-01-01T00:01:00Z, _field: "example-field", _value: 4, foo: "bar"},
            {_time: 2020-01-01T00:02:00Z, _field: "example-field", _value: 1, foo: "bar"},
        ],
    )
    |> reduce(
            fn: (r, accumulator) => ({tag:accumulator.tag + "\"" + r.foo,
                                    field : accumulator.field + "\"" + string(v:r._value)
                                    }),
            identity: {tag: "{example-tag-key:[",
                    field: "example-field:[" }
    )
    |> yield(name: "output of reduce")
    |> map(fn: (r) => ({ r with tag: r.tag + "]" }))
    |> map(fn: (r) => ({ r with field: r.field + "]}" }))
    |> map(fn: (r) => ({ r with final: r.tag + " , " + r.field}))
    |> yield(name: "final JSON")
    |> findRecord(
        fn: (key) => true,
        idx: 0,
        )

http.post(
    url: "https://ptsv2.com/t/c4x38-1656014222/post",
    headers: {"Content-type": "application/json"},
    data: bytes(v: data.final),
    )
```
| field | tag |
| --- | --- |
| field | tag |
| example-field:["3"4"1 | {example-tag-key:["bar"bar"bar |

| field | tag | final |
| --- | --- | --- |
| field | tag | final |
| example-field:["3"4"1 | {example-tag-key:["bar"bar"bar | {example-tag-key:["bar"bar"bar] , example-field:["3"4"1]} |