CODEWITHSUNDEEP
flowtype
scyclow
scyclow

Reputation: 73

Is there some way to specify a "not" type in flow?

Is there some way to specify a "not" type in flow? For example, compact = (input: Array<any>): Array<notFalsey> => input.filter(i => !!i);?

Upvotes: 1

Views: 359

Answers (1)

Gabe Levi
Gabe Levi

Reputation: 1937

Currently, there is no syntax to specify a "not" type, like $Not<string>, which would be anything but a string.

For your specific compact example, Flow's library definition for Array.prototype.filter does include a special case for using the Boolean function as the filter function. So you can write

const compactedArray = myArray.filter(Boolean);

v0.31.0 will ship with a magic type $NonMaybeType, so you will be able to write a compact function with return type Array<$NonMaybeType<T>>.

Upvotes: 4

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