Explain TypeScript Type Assertions Clearly

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• Type assertions instruct the TypeScript compiler to treat a value as a specified type. It uses the as keyword to do so:

• expression as targetType

• type assertion is also known as type narrowing. It allows you to narrow a type from a union type. Let’s see the following simple function:

• number | string

• let netPrice = getNetPrice(100, 0.05, true) as string;

• let netPrice = getNetPrice(100, 0.05, false) as number

• Note that a type assertion does not carry any type casting. It only tells the compiler which type it should apply to a value for the type checking purposes.

• <targetType> value

• let netPrice = <number>getNetPrice(100, 0.05, false);

• Note that you cannot use angle bracket syntax <> with some libraries such as React. For this reason, you should use the as keyword for type assertions.

• ype assertions use the as keyword or an angle bracket <> syntax.