# Ambient Declarations As we mentioned in [why TypeScript](/typescript/getting-started/why-typescript.md): > A major design goal of TypeScript was to make it possible for you to safely and easily use existing JavaScript libraries in TypeScript. TypeScript does this by means of *declaration*. Ambient declarations allow you to *safely use existing popular JavaScript libraries* and *incrementally migrate your JavaScript/CoffeeScript/Other-Compile-To-Js-Language project to TypeScript*. Studying patterns in ambient declarations for *third party JavaScript code* is good practice for annotating *your* TypeScript code base as well. This is why we present it so early on. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://basarat.gitbook.io/typescript/type-system/intro.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.