Add new key value pair to JSON file in powershell.

Question

I have an existing JSON file with the following:

{
    "buildDate":  "2017-08-16",
    "version":  "v1.2.0"
}

How do you add new key-value pairs to an existing JSON file? For example, I would like to take the above JSON, and end up with this:

{
    "buildDate":  "2017-08-16",
    "version":  "v1.2.0",
    "newKey1": "newValue1",
    "newKey2": "newValue2"
}

I currently write to JSON with the following code:

@{buildDate="2017-08-16"; version="v1.2.0"} | ConvertTo-Json | Out-File .\data.json

Solution

Convert the JSON data to a PowerShell object, add the new properties, then convert the object back to JSON:

$jsonfile = 'C:\path\to\your.json'

$json = Get-Content $jsonfile | Out-String | ConvertFrom-Json

$json | Add-Member -Type NoteProperty -Name 'newKey1' -Value 'newValue1'
$json | Add-Member -Type NoteProperty -Name 'newKey2' -Value 'newValue2'

$json | ConvertTo-Json | Set-Content $jsonfile