How to create a JSON object with array in Powershell

Question

I am a newbie to Powershell and I couldn't find this on googling but how do I build a json structure with an array inside? Is it through a custom object? Have been a bit confused by the syntax that I have seen online and not sure what is the recommended way to do it. Eventually I need to be able to save it to a JSON file too.

json_ret = { 
             "a": 4, 
             "b": [ {"c" : 5, "d": "text", "e": "foo"}] 
           }

What do you mean? Do you have JSON that you want to convert into a PowerShell object? Do you want to make an object in PowerShell that you can then turn into a JSON string? Are you just confused by JSON syntax? — Bacon Bits, Jul 17 '20 at 00:03
I need a way to construct a JSON object in powershell and then save it to a file. The format above is an example. I am not clear on how to handle arrays — user2399453, Jul 17 '20 at 00:43

score 6 · Accepted Answer · answered Jul 17 '20 at 00:52

Yes you can build a json object through a PSCustomObject:

[PSCustomObject]@{
  a = 4
  b = @([ordered]@{
    c = 5
    d = "text"
    e = "foo"
  })
} | ConvertTo-Json

First we create PSObject using its type accelerator PSCustomObject.
Then we define the root key and value "a", and we have to create an array inside "b".
The @() statement creates an array, but we can't we create key-value pairs in array. So we use @{} to create hashtable. Before it [ordered] flag says the hashtable to keep the exact structure as we have created it.
Then we define the array values, and after that close the internal array-hashtable.
Now we end the PSCustomObject and pipe it ConvertTo-Json. Now you get a converted json.

Footnotes

If you want to dump the json to a file, then use this:

[PSCustomObject]@{
  a = 4
  b = @([ordered]@{
    c = 5
    d = "text"
    e = "foo"
  })
} | ConvertTo-Json |  Out-File "Filepath"

If you want to save json to a variable:

$variable = ([PSCustomObject]@{
  a = 4
  b = @([ordered]@{
    c = 5
    d = "text"
    e = "foo"
  })
} | ConvertTo-Json)

mklement0 · Answer 2 · 2020-07-18T22:44:24.017

If you want to create the JSON document directly, as a string, it's simplest to use a verbatim here-string:

$json_ret = @'
{ 
  "a": 4, 
  "b": [ {"c" : 5, "d": "text", "e": "foo"}] 
}
'@

You can easily save that to a file with $json_ret | Set-Content file.json, for instance.

By contrast, if you want to construct your data as an object graph first, to be converted to JSON with ConvertTo-Json later, see Wasif_Hasan's helpful answer.

As for what you tried:

An unquoted { ... } construct is a script block, which is a piece of PowerShell code for later invocation on demand - and the contents of your JSON document happen not to constitute valid PowerShell code, causing construction of the script block to fail.

score 2 · Answer 3 · answered Jan 11 '23 at 18:52

If using variables, then can create body including array like shown below, where $text is the variable. No need to user ConvertTo-Json and can easily copy the body from postman directly.

$text = "ABC"

# Post Body
$body = @"
{
        "name" = "$text",
        "description" = "$text",
    "myArray": [
        {
            "id": "2c91808680d3c34b0180dc81d78c21e9",
            "type": "myType",
            "name": "myName"
        }
    ]
}
"@
                
$body

How to create a JSON object with array in Powershell

3 Answers3