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

Problem

Users want to send data with http.post() but they want to send more than just one point at a time, as shown in the following example.

Solution

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

1. Boilerplate. Import packages. The array package is used to construct tables so you can run this script yourself. The http package is used to transfer the JSON over http.

2. Construct a table with the array.from() function. You could also query for your own data.

3. Use the reduce() function to start constructing a JSON. The output of reduce is stored in the result output of reduce. This table looks like:

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

4. Next, use the map() function to combine the two components together to complete our JSON and store it in the column final. Use a second yield() function to store the result 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. This example usest the Post Test Server to grab a URL to dump the JSON 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),
    )