docs-v2/content/resources/how-to-guides/reduce-to-construct-JSON.md

title	description	menu	weight
Using reduce() to construct a JSON.	Learn how to send multiple points with `http.post()` by creating a JSON object with `reduce()`.	resources parent How-to guides	105

Send data in JSON body with http.post()

Use the reduce() function to create a JSON object to include as the body with http.post().

1. Import both the array package to query data and construct table(s), and the http package 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.

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() function to combine the two components together 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 sent the JSON to. In this example, we use Post Test Server as URL to send the JSON to, and test the http.post() function.

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),
    )