Function Parameter Bivariance When comparing the types of function parameters, assignment succeeds if either the source parameter is assignable to the target parameter, or vice versa. This is unsound because a caller might end up being given a function that takes a more specialized type, but invokes the function with a less specialized type. In practice, this sort of error is rare, and allowing this enables many common JavaScript patterns. A brief example: enum EventType { Mouse, Keyboard } in

// Type definitions for [~THE LIBRARY NAME~] [~OPTIONAL VERSION NUMBER~] // Project: [~THE PROJECT NAME~] // Definitions by: [~YOUR NAME~] <[~A URL FOR YOU~]> /*~ This is the global-modifying module template file. You should rename it to index.d.ts *~ and place it in a folder with the same name as the module. *~ For example, if you were writing a file for "super-greeter", this *~ file should be 'super-greeter/index.d.ts' */ /*~ Note: If your global-modifying module is callable or co

Multi-file namespaces Here, we’ll split our Validation namespace across many files. Even though the files are separate, they can each contribute to the same namespace and can be consumed as if they were all defined in one place. Because there are dependencies between files, we’ll add reference tags to tell the compiler about the relationships between the files. Our test code is otherwise unchanged. Validation.ts namespace Validation { export interface StringValidator { isAcceptable(s: str

Using --noResolve Normally the compiler will attempt to resolve all module imports before it starts the compilation process. Every time it successfully resolves an import to a file, the file is added to the set of files the compiler will process later on. The --noResolve compiler options instructs the compiler not to “add” any files to the compilation that were not passed on the command line. It will still try to resolve the module to files, but if the file as not specified, it will not be inc

/// <amd-dependency /> Note: this directive has been deprecated. Use import "moduleName"; statements instead. /// <amd-dependency path="x" /> informs the compiler about a non-TS module dependency that needs to be injected in the resulting module’s require call. The amd-dependency directive can also have an optional name property; this allows passing an optional name for an amd-dependency: /// <amd-dependency path="legacy/moduleA" name="moduleA"/> declare var moduleA:MyType

Watchify We’ll start with Watchify to provide background compilation: npm install --save-dev watchify gulp-util Now change your gulpfile to the following: var gulp = require("gulp"); var browserify = require("browserify"); var source = require('vinyl-source-stream'); var watchify = require("watchify"); var tsify = require("tsify"); var gutil = require("gulp-util"); var paths = { pages: ['src/*.html'] }; var watchedBrowserify = watchify(browserify({ basedir: '.', debug: true, entries:

Using tsconfig.json By invoking tsc with no input files, in which case the compiler searches for the tsconfig.json file starting in the current directory and continuing up the parent directory chain. By invoking tsc with no input files and a --project (or just -p) command line option that specifies the path of a directory containing a tsconfig.json file. When input files are specified on the command line, tsconfig.json files are ignored.

// Type definitions for [~THE LIBRARY NAME~] [~OPTIONAL VERSION NUMBER~] // Project: [~THE PROJECT NAME~] // Definitions by: [~YOUR NAME~] <[~A URL FOR YOU~]> /*~ This is the module template file for function modules. *~ You should rename it to index.d.ts and place it in a folder with the same name as the module. *~ For example, if you were writing a file for "super-greeter", this *~ file should be 'super-greeter/index.d.ts' */ /*~ Note that ES6 modules cannot directly export callab

Symbol.replace A regular expression method that replaces matched substrings of a string. Called by the String.prototype.replace method.

/// <reference path="..." /> The /// <reference path="..." /> directive is the most common of this group. It serves as a declaration of dependency between files. Triple-slash references instruct the compiler to include additional files in the compilation process. They also serve as a method to order the output when using --out or --outFile. Files are emitted to the output file location in the same order as the input after preprocessing pass.