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.

Contextual Type Type inference also works in “the other direction” in some cases in TypeScript. This is known as “contextual typing”. Contextual typing occurs when the type of an expression is implied by its location. For example: window.onmousedown = function(mouseEvent) { console.log(mouseEvent.buton); //<- Error }; For the code above to give the type error, the TypeScript type checker used the type of the Window.onmousedown function to infer the type of the function expression on the

Create a webpack configuration file Create a webpack.config.js file at the root of the project directory. module.exports = { entry: "./src/index.tsx", output: { filename: "./dist/bundle.js", }, // Enable sourcemaps for debugging webpack's output. devtool: "source-map", resolve: { // Add '.ts' and '.tsx' as resolvable extensions. extensions: ["", ".webpack.js", ".web.js", ".ts", ".tsx", ".js"] }, module: { loaders: [ // All files with a '.ts' or '.tsx' ex

Consuming Dependencies There are several kinds of dependencies you might have.

Decorator Composition Multiple decorators can be applied to a declaration, as in the following examples: On a single line: @f @g x On multiple lines: @f @g x When multiple decorators apply to a single declaration, their evaluation is similar to function composition in mathematics. In this model, when composing functions f and g, the resulting composite (f ∘ g)(x) is equivalent to f(g(x)). As such, the following steps are performed when evaluating multiple decorators on a single declarat

Generic Constraints If you remember from an earlier example, you may sometimes want to write a generic function that works on a set of types where you have some knowledge about what capabilities that set of types will have. In our loggingIdentity example, we wanted to be able to access the .length property of arg, but the compiler could not prove that every type had a .length property, so it warns us that we can’t make this assumption. function loggingIdentity<T>(arg: T): T { console.lo

Constructor functions When you declare a class in TypeScript, you are actually creating multiple declarations at the same time. The first is the type of the instance of the class. class Greeter { greeting: string; constructor(message: string) { this.greeting = message; } greet() { return "Hello, " + this.greeting; } } let greeter: Greeter; greeter = new Greeter("world"); console.log(greeter.greet()); Here, when we say let greeter: Greeter, we’re using Greeter as the type of

Consuming From there you’ll be able to use lodash in your TypeScript code with no fuss. This works for both modules and global code. For example, once you’ve npm install-ed your type declarations, you can use imports and write import * as _ from "lodash"; _.padStart("Hello TypeScript!", 20, " "); or if you’re not using modules, you can just use the global variable _. _.padStart("Hello TypeScript!", 20, " ");

const declarations const declarations are another way of declaring variables. const numLivesForCat = 9; They are like let declarations but, as their name implies, their value cannot be changed once they are bound. In other words, they have the same scoping rules as let, but you can’t re-assign to them. This should not be confused with the idea that the values they refer to are immutable. const numLivesForCat = 9; const kitty = { name: "Aurora", numLives: numLivesForCat, } // Error kitty

Code Generation for Modules Depending on the module target specified during compilation, the compiler will generate appropriate code for Node.js (CommonJS), require.js (AMD), isomorphic (UMD), SystemJS, or ECMAScript 2015 native modules (ES6) module-loading systems. For more information on what the define, require and register calls in the generated code do, consult the documentation for each module loader. This simple example shows how the names used during importing and exporting get translat