Bicep spread operator

The spread operator is used to expand an iterable array or object into individual elements. The spread operator allows you to easily manipulate arrays or objects by spreading their elements or properties into new arrays or objects.

Spread

...

The spread operator is used to copy properties from one object to another or to merge arrays and objects in a concise and readable way.

Examples

The following example shows the spread operator used in an object:

var objA = { bar: 'bar' }
output objB object = { foo: 'foo', ...objA } 

Output from the example:

Name	Type	Value
objB	object	{ foo: 'foo', bar: 'bar' }

The following example shows the spread operator used in an array:

var arrA = [ 2, 3 ]
output arrB array = [ 1, ...arrA, 4 ] 

Output from the example:

Name	Type	Value
arrB	array	[ 1, 2, 3, 4 ]

The following example shows spread used multiple times in a single operation:

var arrA = [ 2, 3 ]
output arrC array = [ 1, ...arrA, 4, ...arrA ] 

Output from the example:

Name	Type	Value
arrC	array	[ 1, 2, 3, 4, 2, 3 ]

The following example shows spread used in a multi-line operation:

var objA = { foo: 'foo' }
var objB = { bar: 'bar' }
output combined object = { 
  ...objA
  ...objB
} 

In this usage, comma isn't used between the two lines. Output from the example:

Name	Type	Value
combined	object	{ foo: 'foo', bar: 'bar' }

The spread operation can be used to avoid setting an optional property. For example:

param vmImageResourceId string = ''

var bar = vmImageResourceId != '' ? {
  id: vmImageResourceId
} : {}

output foo object = {
  ...bar
  alwaysSet: 'value'
}

Output from the example:

Name	Type	Value
foo	object	{"alwaysSet":"value"}

The preceding example can also be written as:

param vmImageResourceId string = ''

output foo object = {
  ...(vmImageResourceId != '' ? {
    id: vmImageResourceId
  } : {})
  alwaysSet: 'value'
}

Next steps

• To run the examples, use Azure CLI or Azure PowerShell to deploy a Bicep file.
• To create a Bicep file, see Quickstart: Create Bicep files with Visual Studio Code.
• For information about how to resolve Bicep type errors, see Any function for Bicep.