Type Annotations Can Only Be Used in TypeScript Files
November 6, 2023
Type annotations are one of TypeScript's superpowers. They provide a way to declare the type of a variable, function parameter, function return type, and other constructs. This can drastically improve code clarity, prevent type-related bugs, and aid in refactoring.
What is a Type Annotation?
In TypeScript, a type annotation is a way to explicitly specify the type of a variable, function, or property. It follows the pattern:
Before we delve deeper, let's clarify the difference between
.ts files can you use TypeScript-specific syntax, such as type annotations.
If you attempt to use type annotations in a
.js file, you will encounter a syntax error. Here's why:
The Solution: Convert
If you want to use type annotations (or any other TypeScript features) in a file, you'll need to rename the file from
.ts. Once it's a TypeScript file, you can freely add type annotations.
Here's an example:
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