Is there a way to use shorthand for nullable return types in TypeScript similar to using "name?: type" for parameters?
function veryUsefulFunction(val?: string /* this is OK */)
// but not this or other things I've tried.
// is there a way aside from "|undefined"?
: string?
{
return val?.toLowerCase();
}
There is no way to specify an optional return type in TypeScript. This topic has been debated on the TypeScript issues list but ultimately rejected.
In most cases, you can omit the return type and let TypeScript infer it. However, if you want to explicitly define the return type to avoid accidental changes, you can use string | undefined:
function veryUsefulFunction(val?: string) { // Infers `string | undefined`
return val?.toLowerCase();
}
You can also use string | void or a generic type like Optional<T>, which some libraries offer as a way to represent optional types.
If you'd like to learn more, check out this Playground link for examples.
Sorry, but the return type does not allow the use of the ? operator to suggest that it could possibly be undefined
Instead, the appropriate return type in this case would be:
string | undefined
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