Gulp If you’re using Gulp in some fashion, we have a tutorial on using Gulp with TypeScript, and integrating with common build tools like Browserify, Babelify, and Uglify. You can read more there.

Add TypeScript The next step is to add a folder for TypeScript. We’ll just call it src.

Symbol.toStringTag A String value that is used in the creation of the default string description of an object. Called by the built-in method Object.prototype.toString.

Add example code Type the following code into app.ts. function sayHello() { const compiler = (document.getElementById("compiler") as HTMLInputElement).value; const framework = (document.getElementById("framework") as HTMLInputElement).value; return `Hello from ${compiler} and ${framework}!`; }

Validators in a single file interface StringValidator { isAcceptable(s: string): boolean; } let lettersRegexp = /^[A-Za-z]+$/; let numberRegexp = /^[0-9]+$/; class LettersOnlyValidator implements StringValidator { isAcceptable(s: string) { return lettersRegexp.test(s); } } class ZipCodeValidator implements StringValidator { isAcceptable(s: string) { return s.length === 5 && numberRegexp.test(s); } } // Some samples to try let strings = ["Hello", "98052", "101"]; /

Definition File Theory: A Deep Dive Structuring modules to give the exact API shape you want can be tricky. For example, we might want a module that can be invoked with or without new to produce different types, has a variety of named types exposed in a hierarchy, and has some properties on the module object as well. By reading this guide, you’ll have the tools to write complex definition files that expose a friendly API surface. This guide focuses on module (or UMD) libraries because the optio

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Using with export = or import An important rule is that export and import declarations export or import all meanings of their targets.

Use Optional Parameters Don’t write several overloads that differ only in trailing parameters: /* WRONG */ interface Moment { diff(b: MomentComparable): number; diff(b: MomentComparable, unitOfTime: string): number; diff(b: MomentComparable, unitOfTime: string, round: boolean): number; } Do use optional parameters whenever possible: /* OK */ interface Moment { diff(b: MomentComparable, unitOfTime?: string, round?: boolean): number; } Note that this collapsing should only occur when al

Module Resolution Strategies There are two possible module resolution strategies: Node and Classic. You can use the --moduleResolution flag to specify the module resolution strategy. The default if not specified is Node.