Typescript Programming Tutorials, Guides & Best Practices

type ReturnType<T> = T extends (...args: any[]) => infer R ? R : any;

type FunctionReturnType = ReturnType<() => string>; // string

Union and intersection types enable you to combine multiple types into one, either by allowing any of the types (union) or requiring all of them (intersection).

In this example, Readonly makes every property in the Todo interface read-only.

Conditional types allow you to express types that depend on a condition.

VS Code extensions often start by adding new commands. Let’s create a simple command that displays a message when executed.

In the src/extension.ts file, you'll see that a sample command has already been registered. We’ll modify it to create our own custom command:

npm install --save-dev webpack webpack-cli ts-loader

Then, create a webpack.config.js file:

{
  "compilerOptions": {
    "strict": true,
    "esModuleInterop": true,
    "module": "commonjs",
    "target": "es6",
    "outDir": "./dist",
    "rootDir": "./src"
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules"]
}

The first step in converting your JavaScript project to TypeScript is renaming your JavaScript files. For each .js file in your src directory, rename it to .ts. For example, index.js should become index.ts.