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TypeScript 4.0 Beta

by DanRosenwasser on 6/26/20, 5:01 PM with 17 comments

• by eloff on 6/26/20, 5:49 PM

  Looks like some improvements to spread operators and tuples, which is welcome.

  I'm most excited about: TypeScript 4.0 supports a promising proposal to add three new assignment operators: &&=, ||=, and ??=.

  Which is a nice shortcut for operators I use often.

  No huge changes here that I can see, just small steady improvements to an already excellent language.

• by nammi on 6/26/20, 5:59 PM

  I'm a bit paranoid about upgrading after breaking changes in 3.9 removed the ability to stub ES imports with Sinon/Jasmine/etc..., since the section of the release notes made it sound pretty innocuous: "Getters/Setters are No Longer Enumerable".

  https://github.com/microsoft/TypeScript/issues/38568 https://github.com/microsoft/TypeScript/pull/32264

• by mpawelski on 6/26/20, 9:54 PM

  This release will be great. Lots of people were waiting for variadic tuple types.

  I love when such "old" feature request is finally added to Typescript. First proposal for it was almost 5 years ago [1]. It really gives hope for other long standing and heavily upvoded feature requests that maybe we'll get them one day :)

  [1]https://github.com/microsoft/TypeScript/issues/5453

• by tengbretson on 6/26/20, 6:25 PM

  So excited for variadic tuple types. This will be an absolute game changer!

• by seph-reed on 6/26/20, 6:29 PM

  > Properties Overriding Accessors (and vice versa) is an Error

  Not sure I like this. Can definitely imagine the following being a realistic scenario, and see no reason to disallow it:

      class Base {
        public num = 42;
      }
  
      class Child extends Base {
        protected _num = 42;
        // no longer allowed in 4.0
        public get num() { return this._num; }
        public set num(newVal) { 
          alert(`new num ${newVal}`);
          this._num = newVal
        }
      }
  

  Did I misunderstand something?

• by nojvek on 6/26/20, 6:39 PM

  —incremental with —noEmit is kind of a big deal. Really cool.

  We use ts-loader with webpack in transpileOnly mode and a separate tsc invocation for typechecking that runs as a linter i.e noEmit

• by jondubois on 6/26/20, 7:07 PM

  I like TypeScript because it gives me an edge over my competitors. I look forward to Microsoft coming up with more abstractions to further constrain and slow down my competition and keep lowering the productivity bar in my industry - Microsoft was right when they said that TypeScript would make my life easier.