Get specific value from JSON array after comparison using PowerShell?

Question

I want to get specific value once key is matched from JSON array object

Input:

[
    {
        "Id": "19A7A3C4",
        "displayName": "somename",
        "tags": [
            {
                "context": "CONTEXTLESS",
                "key": "apple",
                "value": "10"
            },
            {
                "context": "CONTEXTLESS",
                "key": "orange",
                "value": "20"
            },
            {
                "context": "CONTEXTLESS",
                "key": "grapes",
                "value": "30"
            }
        ]
    },
    {
        "Id": "111111",
        "displayName": "somename",
        "tags": [
            {
                "context": "CONTEXTLESS",
                "key": "cat",
                "value": "10"
            },
            {
                "context": "CONTEXTLESS",
                "key": "cat",
                "value": "20"
            }
        ]
    }
]

I want to get the value of tag where key matches to cat and value matches to 10, I am using below query but getting whole object

$content = Get-Content -Raw -Path "data.json" | ConvertFrom-Json
$content | Where-Object{ $_.tags.key -eq "cat" -and $_.tags.value -eq "10"}

Desired Output: 10

Answer 1

Mathias's answer already shows a clean way to solve the problem.

A similar approach is using the intrinsic method .Where{}:

$tagValues = $content.tags.Where{ $_.key -eq "cat" -and $_.value -eq "10" }.value

$content.tags employs member enumeration to collect all tags properties into an array. .Where{} filters array elements similar to Where-Object. Lastly .value uses member enumeration again to collect the filtered tag values into an array.

Intrinsic methods like .Where{} are supposed to be faster than pipeline commands because they don't involve the overhead of the pipeline machinery.

---

If you want to keep your original query, you have to deal with nested properties.

Use grouping operator () and dot notation to extract a given property:

$tagValues = ($content | Where-Object{ $_.tags.key -eq "cat" -and $_.tags.value -eq "10"}).tags.value

An alternative is Select-Object with parameter -ExpandProperty (alias -Expand), but it doesn't work as straightforward for nested properties (yet):

$tagValues = $content | Where-Object{ $_.tags.key -eq "cat" -and $_.tags.value -eq "10"} |
    Select-Object -Expand tags | Select-Object -Expand value

A more straightforward alternative is ForEach-Object:

$tagValues = $content | Where-Object{ $_.tags.key -eq "cat" -and $_.tags.value -eq "10"} |
    ForEach-Object { $_.tags.value }