Type erasure in TypeScript refers to the process by which the TypeScript compiler removes type annotations and other type-specific constructs from the code during the compilation process, resulting in plain JavaScript that is devoid of TypeScript's static typing features. This is a fundamental aspect of how TypeScript is designed to integrate with JavaScript, which is a dynamically typed language.
Key Points of Type Erasure in TypeScript
Removal of Type Information: When TypeScript code is compiled, all type annotations, interfaces, type aliases, and other type-related information are removed from the output JavaScript code[3][4][5][8]. For example, a TypeScript variable declaration like let age: number = 30; is transpiled to let age = 30; in JavaScript.
JavaScript Compatibility: The primary reason for type erasure is to ensure compatibility with JavaScript. Since JavaScript does not have a type system like TypeScript, the type information is unnecessary and irrelevant at runtime[2][3][4][5].
Runtime Behavior: Because type information is erased, TypeScript cannot enforce type checking at runtime. This means that errors that could be caught by TypeScript at compile time due to type mismatches will not be prevented at runtime if the compiled JavaScript is fed with unexpected types[2][3]. For instance, a function expecting a number but receiving a string will not cause an error until the function tries to perform an operation that is invalid for strings.
Design Choice: The choice of type erasure aligns with TypeScript's goal to extend JavaScript without altering its runtime behavior. It allows developers to leverage TypeScript's type system during development for better tooling and error checking, while seamlessly integrating with any existing JavaScript...
