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Deno upgrade adds WebSocket API

Deno, an alternative JavaScript runtime to Node.js, has been upgraded with capabilities including a WebSocket API and an early version of an automatic restart capability.

Deno 1.4, released September 13, is being called the largest feature release yet. Highlights include a web standard WebSocket API, for communicating with remote servers via the WebSocket protocol, and an integrated file watcher that can be used to restart any script when its dependencies change. To use the file watcher, developers run a script as they normally would but add the --watch flag. The unstable flag also must be used because this feature is not yet stable. 

Additionally, Deno 1.4 offers integrated test coverage, with developers able to run tests with deno test --coverage to get a summary of test coverage. Other new capabilities in Deno 1.4 include:

  • Stricter type checks in --unstable. TypeScript compiler options isolatedModules and importsNotUsedAsValues are now turned on by default.
  • The deno info tool for dependency analysis has been overhauled. Dependency analysis is now faster and less buggy.
  • CSS styling is now supported for console.log.
  • Lint supports complete eslint and typescript-esline recommended rules.
  • The deno doc documentation generator has received new features and fixes, including support for the export {foo}; syntax and reimports of multiple symbols with the same name.
  • The Visual Studio Code extension for Deno has been updated with capabilities such as IntelliSense for imports, providing autocomplete suggestions for module names on 

Developers who already have Deno installed can upgrade by running deno upgrade. Those installing Deno for the first time can use several methods to access it, including the following:

# Using Shell (macOS and Linux):
curl -fsSL | sh
# Using PowerShell (Windows):
iwr -useb | iex

Deno 1.4 source code is available on GitHub.

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