title	description	ms.topic	ms.custom	ms.date
Template functions - objects	Describes the functions to use in an Azure Resource Manager template (ARM template) for working with objects.	conceptual	devx-track-arm-template	01/11/2024

Object functions for ARM templates

Resource Manager provides several functions for working with objects in your Azure Resource Manager template (ARM template):

contains
createObject
empty
intersection
items
json
length
null
union

Tip

We recommend Bicep because it offers the same capabilities as ARM templates and the syntax is easier to use. To learn more, see object functions.

contains

contains(container, itemToFind)

Checks whether an array contains a value, an object contains a key, or a string contains a substring. The string comparison is case-sensitive. However, when testing if an object contains a key, the comparison is case-insensitive.

In Bicep, use the contains function.

Parameters

Parameter	Required	Type	Description
container	Yes	array, object, or string	The value that contains the value to find.
itemToFind	Yes	string or int	The value to find.

Return value

True if the item is found; otherwise, False.

Example

The following example shows how to use contains with different types:

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/array/contains.json":::

The output from the preceding example with the default values is:

Name	Type	Value
stringTrue	Bool	True
stringFalse	Bool	False
objectTrue	Bool	True
objectFalse	Bool	False
arrayTrue	Bool	True
arrayFalse	Bool	False

createObject

createObject(key1, value1, key2, value2, ...)

Creates an object from the keys and values.

The createObject function isn't supported by Bicep. Construct an object by using {}. See Objects.

Parameters

Parameter	Required	Type	Description
key1	No	string	The name of the key.
value1	No	int, boolean, string, object, or array	The value for the key.
more keys	No	string	More names of the keys.
more values	No	int, boolean, string, object, or array	More values for the keys.

The function only accepts an even number of parameters. Each key must have a matching value.

Return value

An object with each key and value pair.

Example

The following example creates an object from different types of values.

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/object/createobject.json":::

The output from the preceding example with the default values is an object named newObject with the following value:

{
  "intProp": 1,
  "stringProp": "abc",
  "boolProp": true,
  "arrayProp": ["a", "b", "c"],
  "objectProp": {"key1": "value1"}
}

empty

empty(itemToTest)

Determines if an array, object, or string is empty.

In Bicep, use the empty function.

Parameters

Parameter	Required	Type	Description
itemToTest	Yes	array, object, or string	The value to check if it's empty.

Return value

Returns True if the value is empty; otherwise, False.

Example

The following example checks whether an array, object, and string are empty.

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/array/empty.json":::

The output from the preceding example with the default values is:

Name	Type	Value
arrayEmpty	Bool	True
objectEmpty	Bool	True
stringEmpty	Bool	True

intersection

intersection(arg1, arg2, arg3, ...)

Returns a single array or object with the common elements from the parameters.

In Bicep, use the intersection function.

Parameters

Parameter	Required	Type	Description
arg1	Yes	array or object	The first value to use for finding common elements.
arg2	Yes	array or object	The second value to use for finding common elements.
more arguments	No	array or object	More values to use for finding common elements.

Return value

An array or object with the common elements.

Example

The following example shows how to use intersection with arrays and objects.

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/array/intersection.json":::

The output from the preceding example with the default values is:

Name	Type	Value
objectOutput	Object	{"one": "a", "three": "c"}
arrayOutput	Array	["two", "three"]

items

items(object)

Converts a dictionary object to an array. See toObject about converting an array to an object.

In Bicep, use the items.

Parameters

Parameter	Required	Type	Description
object	Yes	object	The dictionary object to convert to an array.

Return value

An array of objects for the converted dictionary. Each object in the array has a key property that contains the key value for the dictionary. Each object also has a value property that contains the properties for the object.

Example

The following example converts a dictionary object to an array. For each object in the array, it creates a new object with modified values.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "variables": {
    "copy": [
      {
        "name": "modifiedListOfEntities",
        "count": "[length(items(variables('entities')))]",
        "input": {
          "key": "[items(variables('entities'))[copyIndex('modifiedListOfEntities')].key]",
          "fullName": "[items(variables('entities'))[copyIndex('modifiedListOfEntities')].value.displayName]",
          "itemEnabled": "[items(variables('entities'))[copyIndex('modifiedListOfEntities')].value.enabled]"
        }
      }
    ],
    "entities": {
      "item002": {
        "enabled": false,
        "displayName": "Example item 2",
        "number": 200
      },
      "item001": {
        "enabled": true,
        "displayName": "Example item 1",
        "number": 300
      }
    }
  },
  "resources": [],
  "outputs": {
    "modifiedResult": {
      "type": "array",
      "value": "[variables('modifiedListOfEntities')]"
    }
  }
}

The preceding example returns:

"modifiedResult": {
  "type": "Array",
  "value": [
    {
      "fullName": "Example item 1",
      "itemEnabled": true,
      "key": "item001"
    },
    {
      "fullName": "Example item 2",
      "itemEnabled": false,
      "key": "item002"
    }
  ]
}

The following example shows the array that is returned from the items function.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "variables": {
    "entities": {
      "item002": {
        "enabled": false,
        "displayName": "Example item 2",
        "number": 200
      },
      "item001": {
        "enabled": true,
        "displayName": "Example item 1",
        "number": 300
      }
    },
    "entitiesArray": "[items(variables('entities'))]"
  },
  "resources": [],
  "outputs": {
    "itemsResult": {
      "type": "array",
      "value": "[variables('entitiesArray')]"
    }
  }
}

The example returns:

"itemsResult": {
  "type": "Array",
  "value": [
    {
      "key": "item001",
      "value": {
        "displayName": "Example item 1",
        "enabled": true,
        "number": 300
      }
    },
    {
      "key": "item002",
      "value": {
        "displayName": "Example item 2",
        "enabled": false,
        "number": 200
      }
    }
  ]
}

[!INCLUDE JSON object ordering]

json

json(arg1)

Converts a valid JSON string into a JSON data type.

In Bicep, use the json function.

Parameters

Parameter	Required	Type	Description
arg1	Yes	string	The value to convert to JSON. The string must be a properly formatted JSON string.

Return value

The JSON data type from the specified string, or an empty value when null is specified.

Remarks

If you need to include a parameter value or variable in the JSON object, use the format function to create the string that you pass to the function.

You can also use null() to get a null value.

Example

The following example shows how to use the json function. Notice that you can pass in null for an empty object.

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/object/json.json":::

The output from the preceding example with the default values is:

Name	Type	Value
emptyObjectOutput	Boolean	True
objectOutput	Object	{"a": "b"}
stringOutput	String	test
booleanOutput	Boolean	True
intOutput	Integer	3
arrayOutput	Array	[ 1, 2, 3 ]
concatObjectOutput	Object	{ "a": "demo value" }

length

length(arg1)

Returns the number of elements in an array, characters in a string, or root-level properties in an object.

In Bicep, use the length function.

Parameters

Parameter	Required	Type	Description
arg1	Yes	array, string, or object	The array to use for getting the number of elements, the string to use for getting the number of characters, or the object to use for getting the number of root-level properties.

Return value

An int.

Example

The following example shows how to use length with an array and string:

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/array/length.json":::

The output from the preceding example with the default values is:

Name	Type	Value
arrayLength	Int	3
stringLength	Int	13
objectLength	Int	4

null

null()

Returns null.

The null function isn't available in Bicep. Use the null keyword instead.

Parameters

The null function doesn't accept any parameters.

Return value

A value that is always null.

Example

The following example uses the null function.

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/object/null.json":::

The output from the preceding example is:

Name	Type	Value
emptyOutput	Bool	True

union

union(arg1, arg2, arg3, ...)

Returns a single array or object with all elements from the parameters. For arrays, duplicate values are included once. For objects, duplicate property names are only included once.

In Bicep, use the union function.

Parameters

Parameter	Required	Type	Description
arg1	Yes	array or object	The first value to use for joining elements.
arg2	Yes	array or object	The second value to use for joining elements.
more arguments	No	array or object	More values to use for joining elements.

Return value

An array or object.

Remarks

The union function uses the sequence of the parameters to determine the order and values of the result.

For arrays, the function iterates through each element in the first parameter and adds it to the result if it isn't already present. Then, it repeats the process for the second parameter and any additional parameters. If a value is already present, its earlier placement in the array is preserved.

For objects, property names and values from the first parameter are added to the result. For later parameters, any new names are added to the result. If a later parameter has a property with the same name, that value overwrites the existing value. The order of the properties isn't guaranteed.

The union function merges not only the top-level elements but also recursively merging any nested arrays and objects within them. See the second example in the following section.

Example

The following example shows how to use union with arrays and objects:

:::code language="json" source="~/resourcemanager-templates/azure-resource-manager/functions/array/union.json":::

The output from the preceding example with the default values is:

Name	Type	Value
objectOutput	Object	{"one": "a", "two": "b", "three": "c2", "four": "d", "five": "e"}
arrayOutput	Array	["one", "two", "three", "four"]

The following example shows the deep merge capability:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "variables": {
    "firstObject": {
      "property": {
        "one": "a",
        "two": "b",
        "three": "c1"
      },
      "nestedArray": [
        1,
        2
      ]
    },
    "secondObject": {
      "property": {
        "three": "c2",
        "four": "d",
        "five": "e"
      },
      "nestedArray": [
        3,
        4
      ]
    },
    "firstArray": [
      [
        "one",
        "two"
      ],
      [
        "three"
      ]
    ],
    "secondArray": [
      [
        "three"
      ],
      [
        "four",
        "two"
      ]
    ]
  },
  "resources": [],
  "outputs": {
    "objectOutput": {
      "type": "Object",
      "value": "[union(variables('firstObject'), variables('secondObject'))]"
    },
    "arrayOutput": {
      "type": "Array",
      "value": "[union(variables('firstArray'), variables('secondArray'))]"
    }
  }
}

The output from the preceding example is:

Name	Type	Value
objectOutput	Object	{"property":{"one":"a","two":"b","three":"c2","four":"d","five":"e"},"nestedArray":[3,4]}
arrayOutput	Array	[["one","two"],["three"],["four","two"]]

If nested arrays were merged, then the value of objectOutput.nestedArray would be [1, 2, 3, 4], and the value of arrayOutput would be [["one", "two", "three"], ["three", "four", "two"]].

Next steps

For a description of the sections in an ARM template, see Understand the structure and syntax of ARM templates.

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Object functions for ARM templates

contains

Parameters

Return value

Example

createObject

Parameters

Return value

Example

empty

Parameters

Return value

Example

intersection

Parameters

Return value

Example

items

Parameters

Return value

Example

json

Parameters

Return value

Remarks

Example

length

Parameters

Return value

Example

null

Parameters

Return value

Example

union

Parameters

Return value

Remarks

Example

Next steps