Exists

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( ref, [ts] )

Description

The Exists function returns boolean true if the provided ref exists at the specified timestamp (in the case of a document), or is non-empty (in the case of a set), and false otherwise.

Parameters

Argument Type Definition and Requirements

ref

Reference

The reference identifier within the database that uniquely identifies a document.

ts

Integer or Timestamp

Optional - The timestamp at which the existence of the ref is checked. Can be expressed as either a number of UNIX microseconds since epoch, or as a Timestamp. Defaults to the current time.

For large values of ts (positive or negative), you may need to express the value in a string to maintain numeric precision (Fauna uses 64-bit signed integers, whereas JavaScript uses 53-bit signed integers).

Returns

A boolean value

Examples

The following query checks for the existence of a ref pointing at a document in the spells collection at value 181388642046968320L. Since this ref is present at the current time, true is returned.

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client.query(
  q.(
    q.(q.('spells'), '181388642046968320')
  )
)
.then((ret) => console.log(ret))
true

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