# How to upgrade TypeScript.

The files in this directory are mostly from the TypeScript repository. We
currently (unfortunately) have a rather manual process for upgrading TypeScript.
It works like this currently:

1. Checkout typescript repo in a seperate directory.
2. Copy typescript.js into Deno repo
3. Copy d.ts files into dts directory
4. Update `ts_version()` in `cli/build.rs`
   https://github.com/denoland/deno/blob/452693256ce7b607fa0b9454b22c57748f616742/cli/build.rs#L73-L76

So that might look something like this:

```
git clone https://github.com/microsoft/TypeScript.git
cd typescript
git checkout v3.9.7
cp lib/typescript.js ~/src/deno/cli/tsc/00_typescript.js
cp lib/*.d.ts ~/src/deno/cli/dts/
```