Function optional

optional<input, const pattern>(pattern): Chainable<OptionalP<input, pattern>, "optional">
P.optional(subpattern) takes a sub pattern and returns a pattern which matches if the key is undefined or if it is defined and the sub pattern matches its value.

Read the documentation for P.optional on GitHub
Type Parameters
- input
- const pattern extends undefined | null | string | number | bigint | boolean | symbol | readonly [] | readonly [unknown, unknown] | readonly [unknown, unknown] | {
  [k: string]: unknown;
  } | UnknownMatcher | PatternMatcher<input> | {
  readonly [k in string | number | symbol]?: Pattern<Readonly<MergeUnion<Exclude<input, readonly any[] | Primitives | Map<any, any> | Set<any>>>>[k]>
  } | readonly UnknownPattern[] | readonly [UnknownPattern, UnknownPattern] | readonly [UnknownPattern, UnknownPattern]
Parameters
- pattern: pattern
Returns Chainable<OptionalP<input, pattern>, "optional">
Example
```
match(value)
  .with({ greeting: P.optional('Hello') }, () => 'will match { greeting?: "Hello" }')
```
- Defined in node_modules/ts-pattern/dist/patterns.d.ts:75