This TypeScript tutorial explores JavaScript engines like Google's V8 and Mozilla's SpiderMonkey. It explains how to configure the TypeScript compiler, write proper TypeScript code, and use Microsoft's IntelliSense feature. It also covers TypeScript's watch mode and warns against installing TypeScript globally. Troubleshooting tips are provided, along with a link to the source code on GitHub.
TypeScript is a superset of JavaScript, so you can use regular JavaScript code in a TypeScript application. This means you can start with your existing JavaScript codebase and gradually migrate it to TypeScript. You can also use legacy JavaScript libraries and frameworks without any issues.
An assertion function is a runtime check that identifies the type of unknown input. TypeScript's compiler assumes the input is of the type claimed by the assertion function's signature. Assertion functions are useful for uncertain values, like user input, and generate runtime checks. They can raise errors if the input doesn't meet criteria.
TypeScript 2.1 introduced mapped types, which allow you to create new types based on the properties of an existing type. For example, you can create a mapped type that has the same keys as an existing type, but with optional values.
TypeScript 3.4 introduced const assertions, which allow you to claim a value as immutable. This is useful when working with arrays, as it prevents new values from being added to an existing array.