array.firstWhere()

This method operates on an array. You typically fetch documents from a collection as a set, not an Array. For the equivalent Set method, see set instance methods.

For differences between Sets and Arrays, see Sets vs. Arrays.

Get the first element of an Array that matches a provided predicate.

Signature

firstWhere(predicate: (A => Boolean | Null)) => A | Null

Description

Gets the first element of the calling Array that matches a provided predicate function.

Parameters

Parameter Type Required Description

predicate

Predicate function

Yes

Anonymous predicate function that:

  • Accepts an Array element as its only argument. You can pass in this argument using arrow function syntax. Supports shorthand-syntax for objects and documents.

  • Returns Boolean or Null.

The method returns the first Array element for which the predicate returns true.

Return value

One of:

Type Description

Generic

First element of the Array that matches the predicate.

Null

Returned if no Array element matches the predicate or the Array is empty.

Examples

let iter = [1, 2, 3, 4]
iter.firstWhere(v => v > 2)
3

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