== Why is this an issue?

Having default value for optional boolean parameters makes the logic of function when missing that parameter more evident. When providing a default value is not possible, it is better to split the function into two with a clear responsibility separation.


=== Noncompliant code example

[source,javascript]
----
function countPositiveNumbers(arr: number[], countZero?: boolean) { // Noncompliant, default value for 'countZero' should be defined
  // ...
}

function toggleProperty(property: string, value?: boolean) { // Noncompliant, a new function should be defined
  if (value !== undefined) {
    setProperty(property, value);
  } else {
    setProperty(property, calculateProperty());
  }
}
----


=== Compliant solution

[source,javascript]
----
function countPositiveNumbers(arr: number[], countZero = false) {
  // ...
}

function toggleProperty(property: string, value: boolean) {
  setProperty(property, value);
}

function togglePropertyToCalculatedValue(property: string) {
  setProperty(property, calculateProperty());
}
----

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Provide a default value for 'xxx' so that the logic of the function is more evident when this parameter is missing. Consider defining another function if providing default value is not possible.


=== Highlighting

Entire parameter with type


endif::env-github,rspecator-view[]