Learning TypeScript 2.x - Second Edition

Ambient declarations

The ambient declaration allows you to create a variable in your TypeScript code that will not be translated into JavaScript at compilation time. This feature was designed to make the integration with the existing JavaScript code and the Document Object Model (DOM) and Browser Object Model (BOM) easier. Let's look at an example:

customConsole.log("A log entry!");  // error

If you try to call the member log of an object named customConsole, TypeScript will let us know that the customConsole object has not been declared:

// Cannot find name 'customConsole'

This is not a surprise. However, sometimes we want to invoke an object that has not been defined, for example, the console or window objects:

console.log("Log Entry!"); ...