denoland-deno/docs/standard_library.md

Standard library

Deno provides a set of standard modules that are audited by the core team and are guaranteed to work with Deno.

Standard library is available at: https://deno.land/std/

Versioning and stability

Standard library is not yet stable and therefore it is versioned differently than Deno. For latest release consult https://deno.land/std/ or https://deno.land/std/version.ts.

We strongly suggest to always use imports with pinned version of standard library to avoid unintended changes.

Troubleshooting

Some of the modules provided in standard library use unstable Deno APIs.

Trying to run such modules without --unstable CLI flag ends up with a lot of TypeScript errors suggesting that some APIs on Deno namespace do not exist:

// main.ts
import { copy } from "https://deno.land/std@0.50.0/fs/copy.ts";

copy("log.txt", "log-old.txt");

$ deno run --allow-read --allow-write main.ts
Compile file:///dev/deno/main.ts
Download https://deno.land/std@0.50.0/fs/copy.ts
Download https://deno.land/std@0.50.0/fs/ensure_dir.ts
Download https://deno.land/std@0.50.0/fs/_util.ts
error: TS2339 [ERROR]: Property 'utime' does not exist on type 'typeof Deno'.
    await Deno.utime(dest, statInfo.atime, statInfo.mtime);
               ~~~~~
    at https://deno.land/std@0.50.0/fs/copy.ts:90:16

TS2339 [ERROR]: Property 'utimeSync' does not exist on type 'typeof Deno'.
    Deno.utimeSync(dest, statInfo.atime, statInfo.mtime);
         ~~~~~~~~~
    at https://deno.land/std@0.50.0/fs/copy.ts:101:10

Solution to that problem requires adding --unstable flag:

$ deno run --allow-read --allow-write --unstable main.ts

To make sure that API producing error is unstable check lib.deno.unstable.d.ts declaration.

This problem should be fixed in the near future.