Debug In Edge, press F12 and click the Debugger tab. Look in the first localhost folder, then src/app.ts Put a breakpoint on the line with return. Type in the boxes and confirm that the breakpoint hits in TypeScript code and that inspection works correctly. That’s all you need to know to include basic TypeScript in your ASP.NET project. Next we’ll include Angular and write a simple Angular app.

Global-modifying Modules A global-modifying module alters existing values in the global scope when they are imported. For example, there might exist a library which adds new members to String.prototype when imported. This pattern is somewhat dangerous due to the possibility of runtime conflicts, but we can still write a declaration file for it.

Add TypeScript code Right click on src and click New Item. Then choose TypeScript File and name the file app.ts.

Integrating with Build Tools You might have some more build steps in your pipeline. Perhaps you concatenate something to each of your files. Each build tool is different, but we’ll do our best to cover the gist of things.

Using a class as an interface As we said in the previous section, a class declaration creates two things: a type representing instances of the class and a constructor function. Because classes create types, you can use them in the same places you would be able to use interfaces. class Point { x: number; y: number; } interface Point3d extends Point { z: number; } let point3d: Point3d = {x: 1, y: 2, z: 3};

Find and Install Declaration Files For JavaScript library users, the Consumption section offers a few simple steps to locate and install corresponding declaration files.

Putting it all together Just run: tsc Now open up index.html in your favorite browser and everything should be ready to use! You should see a page that says “Hello from TypeScript and Knockout!” Below that, you’ll also see two input boxes. As you modify their contents and switch focus, you’ll see that the original message changes.

Initialize the project Now we’ll turn this folder into an npm package. npm init You’ll be given a series of prompts. You can use the defaults except for your entry point. For your entry point, use ./dist/main.js. You can always go back and change these in the package.json file that’s been generated for you.

Excess Property Checks In our first example using interfaces, TypeScript let us pass { size: number; label: string; } to something that only expected a { label: string; }. We also just learned about optional properties, and how they’re useful when describing so-called “option bags”. However, combining the two naively would let you to shoot yourself in the foot the same way you might in JavaScript. For example, taking our last example using createSquare: interface SquareConfig { color?: string

Global Libraries A global library is one that can be accessed from the global scope (i.e. without using any form of import). Many libraries simply expose one or more global variables for use. For example, if you were using jQuery, the $ variable can be used by simply referring to it: $(() => { console.log('hello!'); } ); You’ll usually see guidance in the documentation of a global library of how to use the library in an HTML script tag: <script src="http://a.great.cdn.for/someLib.js">