FQL v4 will be decommissioned on June 30, 2025. Ensure that you complete your migration from FQL v4 to FQL v10 by that date.

Fauna accounts created after August 21, 2024 must use FQL v10. These accounts will not be able to run FQL v4 queries or access the v4 Dashboard.

For more details, see the v4 EOL announcement and migration guide. Contact support@fauna.com with any questions.

IsNull

This reference topic applies to FQL v4. Go to this page for the latest FQL v10 reference topics.

Copied!
IsNull( value )

Description

The IsNull function returns true only if value is a null, otherwise it returns false.

Parameters

Parameter Type Definition and Requirements

value

Any

Any value, which is to be tested to determine whether it is a null or not.

Returns

Returns a Boolean, indicating whether value was a null or not.

Examples

The following query uses Map to iterate over an array of all of the types of values that can be tested by a type-check function, passing each item into a Lambda function that returns an object, which contains the value and the result of calling IsNull with that value:

Copied!
Map(
  [
    ['array'],
    true,
    false,
    new Uint8Array([1, 2, 3, 4]),
    [0x1, 0x2, 0x3, 0x4],
    Collection('Letters'),
    Ref('credentials/self'),
    Database('child_db'),
    Date('2019-11-12'),
    Ref(Collection('Letters'), 123),
    10.1,
    Function('double'),
    Index('letters'),
    10,
    Ref(Keys(), '1'),
    Query(Lambda('x', Var('x'))),
    null,
    { x: 10 },
    Role('employees'),
    Match(Index('letters')),
    'ten',
    '10',
    Time('2020-07-06T12:34:56.789Z'),
    Ref(Tokens(), '1'),
  ],
  Lambda('x', {
    value: Var('x'),
    IsNull: IsNull(Var('x')),
  })
)
[
  { value: [ 'array' ], IsNull: false },
  { value: true, IsNull: false },
  { value: false, IsNull: false },
  { value: { '0': 1, '1': 2, '2': 3, '3': 4 }, IsNull: false },
  { value: [ 1, 2, 3, 4 ], IsNull: false },
  { value: Collection("Letters"), IsNull: false },
  { value: Ref(Credentials(), "302043979982045696"), IsNull: false },
  { value: Database("child_db"), IsNull: false },
  { value: Date("2019-11-12"), IsNull: false },
  { value: Ref(Collection("Letters"), "123"), IsNull: false },
  { value: 10.1, IsNull: false },
  { value: Function("double"), IsNull: false },
  { value: Index("letters"), IsNull: false },
  { value: 10, IsNull: false },
  { value: Ref(Keys(), "1"), IsNull: false },
  { value: Query(Lambda("x", Var("x"))), IsNull: false },
  { value: null, IsNull: true },
  { value: { x: 10 }, IsNull: false },
  { value: Role("employees"), IsNull: false },
  { value: Match(Index("letters")), IsNull: false },
  { value: 'ten', IsNull: false },
  { value: '10', IsNull: false },
  { value: Time("2020-07-06T12:34:56.789Z"), IsNull: false },
  { value: Ref(Tokens(), "1"), IsNull: false }
]
Query metrics:
  •    bytesIn:   596

  •   bytesOut: 1,535

  • computeOps:     2

  •    readOps:     0

  •   writeOps:     0

  •  readBytes:   373

  • writeBytes:     0

  •  queryTime:  20ms

  •    retries:     0

This query operates on a pre-existing schema, which is not provided here.

Also, the query is executed via a client connection, that uses a secret acquired by calling the Login function (not shown here), so that Ref("credentials/self") returns a valid value.

Is this article helpful? 

Tell Fauna how the article can be improved:
Visit Fauna's forums or email docs@fauna.com

Thank you for your feedback!