Combine JSON objects in PowerShell

Question

I have two JSON objects and I am trying to build one object out of it. I am using an example here, but the properties/names are dynamic.

I have looked into JOIN function, MERGE, Combine-Object none of them seems to do what I want. As they either replace the values with the one or give me random results.

This is my example,

$aVar = '{ "oldEmployees" : [ { "firstName": "Jane", "lastName": "Doe" }, { "firstName": "John", "lastName": "Doe" } ] }'
$bVar = '{ "newEmployees" : [ { "firstName": "Joe", "lastName": "Doe" } ] }'

I would like to have one JSON as,

{
    "oldEmployees": [
        {
            "firstName": "Jane",
            "lastName": "Doe"
        }, 
        {
            "firstName": "John",
            "lastName": "Doe"
        }
    ],
    "newEmployees": [
        {
            "firstName": "Joe",
            "lastName": "Doe"
        }
    ]
}

BACKGROUND: I am using a JSON object to deploy multiple resources in Azure DevOps pipeline using an ARM template. I have hit a point where I am limited to use Powershell script to combine multiple variables due to the size limit on the Azure Pipeline Variables to a max of 4K characters.

Yes, I have to add it in my Azure pipelines and my options are restricted to Powershell script. — PEF
– PEF, Commented Aug 30, 2019 at 10:30
I don't know what went wrong (maybe an older version) but the Join-Object cmdlet, you refer to, gives exactly the results that you would like to have: ($aVar | ConvertFrom-Json) | Join-Object ($bVar | ConvertFrom-Json) | ConvertTo-Json -Compress → {"oldEmployees":[{"firstName":"Jane","lastName":"Doe"},{"firstName":"John","lastName":"Doe"}],"newEmployees":{"firstName":"Joe","lastName":"Doe"}} (See also: Merge two json objects) — iRon
– iRon, Commented Nov 18, 2019 at 9:46

JamesQMurphy · Accepted Answer · 2019-08-30 11:52:03Z

4

This will give you the exact JSON that you seek:

$combinedObject = New-Object -TypeName PSObject -Property @{
    oldEmployees = @($aVar | ConvertFrom-Json | Select-Object -ExpandProperty oldEmployees)
    newEmployees = @($bVar | ConvertFrom-Json | Select-Object -ExpandProperty newEmployees)
} | ConvertTo-Json

It's the same approach as Panomosh's answer, except that instead of using an array, I used a property map. This prevents the output from having an array.

edited Aug 30, 2019 at 11:52

answered Aug 30, 2019 at 10:54

JamesQMurphy

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5 Comments

Panomosh Over a year ago

very nice @JamesQMurphy

PEF Over a year ago

This is great. Thank you so much!

PEF Over a year ago

@JamesQMurphy Okay, the only issue I have with this is, I am not getting $bVar as an array anymore. The output I have is

{ "oldEmployees":   [ { "firstName":  "Jane", "lastName":  "Doe" }, { "firstName":  "John", "lastName":  "Doe" } ], "newEmployees":   { "firstName":  "Joe", "lastName":  "Doe" } }

. Where I want it to be

{ "oldEmployees":   [ { "firstName":  "Jane", "lastName":  "Doe" }, { "firstName":  "John", "lastName":  "Doe" } ], "newEmployees":  ** [**{ "firstName":  "Joe", "lastName":  "Doe" }**]** }

. Even though there is only one employee in it.

PEF Over a year ago

Think it doesn't matter. But wanted to see it consistent. If not, it is okay. I believe it should work. Will keep you posted.

JamesQMurphy Over a year ago

I have updated my answer so that oldEmployees and newEmployees are always arrays

user6811411 · Accepted Answer · 2019-08-30 10:47:30Z

4

Simply pipe your definition to |Convertfrom-Json

$aVar = '{ "oldEmployees" : [ { "firstName": "Jane", "lastName": "Doe" }, { "firstName": "John", "lastName": "Doe" } ] }' |ConvertFrom-Json
$bVar = '{ "newEmployees" : [ { "firstName": "Joe", "lastName": "Doe" } ] }'|ConvertFrom-Json

$aVar,$bVar|ConvertTo-Json

The result is ugly formatted with PSv5 it get's better with core.

[
    {
        "oldEmployees":  [
                             "@{firstName=Jane; lastName=Doe}",
                             "@{firstName=John; lastName=Doe}"
                         ]
    },
    {
        "newEmployees":  [
                             "@{firstName=Joe; lastName=Doe}"
                         ]
    }
]

answered Aug 30, 2019 at 10:47

user6811411

3 Comments

PEF Over a year ago

This is insanely simple. I probably just thought is something more complicated. But it is simple if you know what you are doing. Really appreciate it. :)

Panomosh Over a year ago

I actually did not know you could chain variables like that $aVar,$bVar thanks @LotPings

JamesQMurphy Over a year ago

Note that this still produces an array in the output JSON

Panomosh · Accepted Answer · 2019-08-30 10:44:38Z

you are going to have to turn both of the JSON into powershell objects, combine them, and then turn them back into JSON. In the example above, powershell will just see them as strings.

You can do this like so:

$container = @()
$container += ConvertFrom-Json '{ "oldEmployees" : [ { "firstName": "Jane", "lastName": "Doe" }, { "firstName": "John", "lastName": "Doe" } ] }'
$container += ConvertFrom-Json '{ "newEmployees" : [ { "firstName": "Joe", "lastName": "Doe" } ] }'

$combinedObject = $container | ConvertTo-Json

now if you view $combinedObject you will see:

[
{
    "newEmployees":  [
                         "@{firstName=Joe; lastName=Doe}"
                     ]
},
{
    "oldEmployees":  [
                         "@{firstName=Jane; lastName=Doe}",
                         "@{firstName=John; lastName=Doe}"
                     ]
}
]

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