$$coalesce / $$first

Returns the first non-null value

tip

Coalesce can also be referred to as $$first instead of $$coealesce

Usage

{ 
  "$$coalesce": /* Array of elements (may include nulls) */
}

"$$coalesce:{input}"

{ 
  "$$first": /* Array of elements (may include nulls) */
}

"$$first:{input}"

Returns

Same as first non-null value

Arguments

Argument	Type	Values	Required / Default Value	Description
Primary	array		Yes	Array of elements (may include nulls)

Examples

Input

Definition

Output

[
  null,
  null,
  2
]

{
  "$$coalesce": "$"
}

2

Test

[
  null,
  null,
  2
]

{
  "$$coalesce": [
    "$[0]",
    "b",
    "c"
  ]
}

"b"

Test

[
  null,
  null,
  2
]

{
  "$$first": [
    null,
    null,
    "c"
  ]
}

"c"

Test