Open HelloWorldWebPart.ts located in the src\webparts\helloWorld folder:
If you are unfamiliar with TypeScript, the contents of this file might look a bit scary at first, but believe me, after you get familiar with TypeScript, the contents make more sense than pure JavaScript. TypeScript adds typing information and more expressive notations of ECMAScript 6 that can be used because of how TypeScript can actually compile the JavaScript to follow ECMAScript 5, which in turn can be interpreted by most browsers used today. The main motivation for developers to learn TypeScript is to make JavaScript more accessible, especially for developers coming from a .NET background.
The main program in this web part is actually the render() function, which you might be familiar with if you've previously created classic SharePoint web parts as full-trust solutions.
Let's begin with the import statements.
In TypeScript, import is used to import other...