Type Checking with typeof

This lesson goes over type checking with JavaScript's typeof.

We'll cover the following

Borrowing type

Borrowing the type of another variable is possible by using typeof. Borrowing type brings protection at design time by allowing you to set a type without defining an actual interface or type. For example, you define a variable with some members using curly braces. There is no actual way to get the schema of the object.

However, with typeof, you can extract the type from the variable. The extraction is possible for variables or parameters. Instead of a concrete type, the variable uses typeof followed by the name of the variable to borrow the schema. This technique is called “type aliases”.

The transposition of the returned type from typeof can be in a concrete type by using the type keyword, followed by the name of the type you create by extracting this one from typeof.

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