How to Narrow a Type with the in Operator

This lesson will look at how to use the in operator to narrow a type.

The in operator explained

The in operator can narrow a type from a union. The left part of the operand is a string or a string literal. The right part is a union type. The result is a Boolean that returns true if the union contains the string and false if it doesn’t.

Usage of the in operator explained

Get hands-on with 1200+ tech skills courses.