Inferred Type Predicates


It's finally here! While working with TypeScript, I assume we all have been in a situation where we have to write a type predicate to help TypeScript understand the type of a variable. For most cases this is fine, but it can be a pain to write these while using the filter method.

Now with the TypeScript 5.5 release, TypeScript introduces a new feature called Inferred Type Predicates. This feature allows TypeScript to infer type predicates automatically. This means that TypeScript can now understand the type of a variable or return value based on the conditions that are checked in the code.

Functions that previously required a Type Predicate can now be simplified. This is a great improvement for developers, as it reduces the amount of boilerplate code needed to write type predicates.

Take a look at the following TypeScript playground examples to see the difference between TypeScript 5.5.0-beta and TypeScript 5.4.5.

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