Object functions for ARM templates

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

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:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "stringToTest": {
      "type": "string",
      "defaultValue": "OneTwoThree"
    },
    "objectToTest": {
      "type": "object",
      "defaultValue": {
        "one": "a",
        "two": "b",
        "three": "c"
      }
    },
    "arrayToTest": {
      "type": "array",
      "defaultValue": [ "one", "two", "three" ]
    }
  },
  "resources": [
  ],
  "outputs": {
    "stringTrue": {
      "type": "bool",
      "value": "[contains(parameters('stringToTest'), 'e')]"
    },
    "stringFalse": {
      "type": "bool",
      "value": "[contains(parameters('stringToTest'), 'z')]"
    },
    "objectTrue": {
      "type": "bool",
      "value": "[contains(parameters('objectToTest'), 'one')]"
    },
    "objectFalse": {
      "type": "bool",
      "value": "[contains(parameters('objectToTest'), 'a')]"
    },
    "arrayTrue": {
      "type": "bool",
      "value": "[contains(parameters('arrayToTest'), 'three')]"
    },
    "arrayFalse": {
      "type": "bool",
      "value": "[contains(parameters('arrayToTest'), 'four')]"
    }
  }
}

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.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
  ],
  "outputs": {
    "newObject": {
      "type": "object",
      "value": "[createObject('intProp', 1, 'stringProp', 'abc', 'boolProp', true(), 'arrayProp', createArray('a', 'b', 'c'), 'objectProp', createObject('key1', 'value1'))]"
    }
  }
}

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.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "testArray": {
      "type": "array",
      "defaultValue": []
    },
    "testObject": {
      "type": "object",
      "defaultValue": {}
    },
    "testString": {
      "type": "string",
      "defaultValue": ""
    }
  },
  "resources": [
  ],
  "outputs": {
    "arrayEmpty": {
      "type": "bool",
      "value": "[empty(parameters('testArray'))]"
    },
    "objectEmpty": {
      "type": "bool",
      "value": "[empty(parameters('testObject'))]"
    },
    "stringEmpty": {
      "type": "bool",
      "value": "[empty(parameters('testString'))]"
    }
  }
}

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.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "firstObject": {
      "type": "object",
      "defaultValue": {
        "one": "a",
        "two": "b",
        "three": "c"
      }
    },
    "secondObject": {
      "type": "object",
      "defaultValue": {
        "one": "a",
        "two": "z",
        "three": "c"
      }
    },
    "firstArray": {
      "type": "array",
      "defaultValue": [ "one", "two", "three" ]
    },
    "secondArray": {
      "type": "array",
      "defaultValue": [ "two", "three" ]
    }
  },
  "resources": [
  ],
  "outputs": {
    "objectOutput": {
      "type": "object",
      "value": "[intersection(parameters('firstObject'), parameters('secondObject'))]"
    },
    "arrayOutput": {
      "type": "array",
      "value": "[intersection(parameters('firstArray'), parameters('secondArray'))]"
    }
  }
}

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.

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
      }
    }
  ]
}

In JSON, an object is an unordered collection of zero or more key/value pairs. The ordering can be different depending on the implementations. For example, the Bicep items() function sorts the objects in the alphabetical order. In other places, the original ordering can be preserved. Because of this non-determinism, avoid making any assumptions about the ordering of object keys when writing code, which interacts with deployments parameters & outputs.

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 concat 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.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "jsonEmptyObject": {
      "type": "string",
      "defaultValue": "null"
    },
    "jsonObject": {
      "type": "string",
      "defaultValue": "{\"a\": \"b\"}"
    },
    "jsonString": {
      "type": "string",
      "defaultValue": "\"test\""
    },
    "jsonBoolean": {
      "type": "string",
      "defaultValue": "true"
    },
    "jsonInt": {
      "type": "string",
      "defaultValue": "3"
    },
    "jsonArray": {
      "type": "string",
      "defaultValue": "[[1,2,3 ]"
    },
    "concatValue": {
      "type": "string",
      "defaultValue": "demo value"
    }
  },
  "resources": [
  ],
  "outputs": {
    "emptyObjectOutput": {
      "type": "bool",
      "value": "[empty(json(parameters('jsonEmptyObject')))]"
    },
    "objectOutput": {
      "type": "object",
      "value": "[json(parameters('jsonObject'))]"
    },
    "stringOutput": {
      "type": "string",
      "value": "[json(parameters('jsonString'))]"
    },
    "booleanOutput": {
      "type": "bool",
      "value": "[json(parameters('jsonBoolean'))]"
    },
    "intOutput": {
      "type": "int",
      "value": "[json(parameters('jsonInt'))]"
    },
    "arrayOutput": {
      "type": "array",
      "value": "[json(parameters('jsonArray'))]"
    },
    "concatObjectOutput": {
      "type": "object",
      "value": "[json(concat('{\"a\": \"', parameters('concatValue'), '\"}'))]"
    }
  }
}

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:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "arrayToTest": {
      "type": "array",
      "defaultValue": [
        "one",
        "two",
        "three"
      ]
    },
    "stringToTest": {
      "type": "string",
      "defaultValue": "One Two Three"
    },
    "objectToTest": {
      "type": "object",
      "defaultValue": {
        "propA": "one",
        "propB": "two",
        "propC": "three",
        "propD": {
          "propD-1": "sub",
          "propD-2": "sub"
        }
      }
    }
  },
  "resources": [],
  "outputs": {
    "arrayLength": {
      "type": "int",
      "value": "[length(parameters('arrayToTest'))]"
    },
    "stringLength": {
      "type": "int",
      "value": "[length(parameters('stringToTest'))]"
    },
    "objectLength": {
      "type": "int",
      "value": "[length(parameters('objectToTest'))]"
    }
  }
}

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.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [],
  "outputs": {
    "emptyOutput": {
      "type": "bool",
      "value": "[empty(null())]"
    }
  }
}

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, it's 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.

Example

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

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "firstObject": {
      "type": "object",
      "defaultValue": {
        "one": "a",
        "two": "b",
        "three": "c1"
      }
    },
    "secondObject": {
      "type": "object",
      "defaultValue": {
        "three": "c2",
        "four": "d",
        "five": "e"
      }
    },
    "firstArray": {
      "type": "array",
      "defaultValue": [ "one", "two", "three" ]
    },
    "secondArray": {
      "type": "array",
      "defaultValue": [ "three", "four" ]
    }
  },
  "resources": [
  ],
  "outputs": {
    "objectOutput": {
      "type": "object",
      "value": "[union(parameters('firstObject'), parameters('secondObject'))]"
    },
    "arrayOutput": {
      "type": "array",
      "value": "[union(parameters('firstArray'), parameters('secondArray'))]"
    }
  }
}

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"]

Next steps