1# Read this! 2 3The files within this directory are copied and deployed with TypeScript as the set of APIs available as a part of the JavaScript language. 4 5There are three main domains of APIs in `src/lib`: 6 7 - **ECMAScript language features** - e.g. JavaScript APIs like functions on Array etc which are documented in [ECMA-262](https://tc39.es/ecma262/) 8 - **DOM APIs** - e.g. APIs which are available in web browsers 9 - **Intl APIs** - e.g. APIs scoped to `Intl` which are documented in [ECMA-402](https://www.ecma-international.org/publications-and-standards/standards/ecma-402/) 10 11## How do we figure out when to add something? 12 13TypeScript has a rule-of-thumb to only add something when it has got far enough through the standards process that it is more or less confirmed. For JavaScript APIs and language features, that means the proposal is at stage 3 or later. 14 15You can find the source of truth for modern language features and Intl APIs in these completed proposal lists: 16 17 - [JavaScript](https://github.com/tc39/proposals/blob/master/finished-proposals.md) 18 - [Intl](https://github.com/tc39/proposals/blob/master/ecma402/finished-proposals.md) 19 20For the DOM APIs, which are a bit more free-form, we have asked that APIs are available un-prefixed/flagged in at least 2 browser _engines_ (i.e. not just 2 chromium browsers.) 21 22## Generated files 23 24The DOM files ending in `.generated.d.ts` aren't meant to be edited by hand. 25 26If you need to make changes to such files, make a change to the input files for [**our library generator**](https://github.com/microsoft/TypeScript-DOM-lib-generator). 27