Select Dynamically keys from JSON

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Posted on by CU19121717-0

Hello,

I have an array that contains the keys/columns that I want in my final output that looks like this:

[

"a",

"b",

"c",

"d"

]

Note that this array is dynamic, and can be different each run of the flow. So It can present only 3, 4 or more keys.

Then I have the following

[
{
"a": "Jonh",
"b": "2023-06-01",
"c": No,
"d": "63055571",
"e": "12",
"f": "null",
"g": "red",
"h": "Paris",
"i": "true",
"j": "55.9"
},
{
"a": "Ana",
"b": "2024-06-01",
"c": Yes,
"d": "63073455",
"e": "12",
"f": "null",
"g": "green",
"h": "London",
"i": "false",
"j": "34.5"
},
...
]

Now I need a way to be able to dynamically filter the keys/columns so I have in the second only the columns from the first array like this:

[
{
"a": "Jonh",
"b": "2023-06-01",
"c": No,
"d": "63055571"
},
{
"a": "Ana",
"b": "2024-06-01",
"c": Yes,
"d": "63073455"
},
...
]

And in the end save it to CSV.

The issue here is that i am not finding a way to dynamically filter it to only output the columns on the first array.

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Nived_Nambiar 18,129 Super User 2025 Season 2 on at

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Hi @CU19121717-0

Try this approach which helps to dynmically filter out required keys from json array

1. use initialize variable to define these variables

2. Use apply to each to loop through the JsonArr variable as shown below

Next steps will be inside the loop

2.1 - use set variable to set tempobj variable

2.2 - Use another loop to loop through Array1 variable

Inside the above loop perform the 2 steps as shown below

2.2.1 use addProperty function to add the property to the tempobject variable as shown below using compose action

Expression used:

addProperty(variables('tempobj'),items('Apply_to_each_2'),items('Apply_to_each')?[items('Apply_to_each_2')])

2.2.2 use set variable to update the temp object with output from compose action

Now outside the loop and following the steps as per the inner step (first apply to each)

2.3 Append the tempobject to FinalArray variable as shown below

Now outside of all loops- use a compose action to display the Final Array variable which has required array format data

Final flow looks like below

Output looks like below

Thanks & Regards,
Nived N

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Chriddle 8,436 Super User 2025 Season 2 on at

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My idea is to loop over the keys and add a corresponding property to the objects (which are empty at the start) in a Select:

Select Object0:

{ "inputs": { "from": "@range(0, length(outputs('Compose_Data')))", "select": {} } }

Initialze variable Result:

{ "inputs": { "variables": [ { "name": "Result", "type": "array", "value": "@body('Select_Objects0')" } ] } }

Apply to each Property:

@{outputs('Compose_Keys')}

Select ObjectsN:

{ "inputs": { "from": "@range(0, length(outputs('Compose_Data')))", "select": "@addProperty(variables('Result')[item()], items('Apply_to_each_Property'), outputs('Compose_Data')[item()][items('Apply_to_each_Property')])" } }

Set variable:

{ "inputs": { "from": "@range(0, length(outputs('Compose_Data')))", "select": "@addProperty(variables('Result')[item()], items('Apply_to_each_Property'), outputs('Compose_Data')[item()][items('Apply_to_each_Property')])" } }

Compose:

{ "inputs": "@variables('Result')" }

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Chriddle 8,436 Super User 2025 Season 2 on at

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If you are not scared of using XPath and creating JSON strings, you can achieve the same result as below without loops. Just 3 Selects.

With the same "Compose Keys" and "Compose Data" from below:

Select

From: @{outputs('Compose_Keys')}

Map:

split( concat( '"', item(), '":"', join( xpath( xml(json(concat('{"Root":{"Item":', outputs('Compose_Data'), '}}'))), concat('//Item/',item(),'/text()') ), concat('"|*|"', item(), '":"') ), '"' ), '|*|' )

Select 2

From:

range(1, length(outputs('Compose_Data')))

Map:

xpath( xml(json(concat('{"Root":{"Item":', body('Select'), '}}'))), concat('//Item/Item[', item(), ']/text()') )

Select 3

From: @{body('Select_2')}

Map:

json( concat( '{', join(item(), ','), '}' ) )

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