Support for new.target

[kitsonk]

TypeScript Version:

1.8.10

Code

function Foo() {
  console.log(new.target);
}

new Foo();

Expected behavior:

When targeting ES6, this should compile without an error.

new.target is an obscure bit of ES6, but it is there, for example running the code in an ES6 browser returns what is expected in that new.target === Foo. When it is just Foo() without new then new.target === undefined.

While it maybe challenging to come up with an emit that works for ES5, it should be at least supported when targeting ES6.

I suspect and emit for ES6 might be something like this:

function Foo() {
  var _newTarget = this === window ? undefined : this && this.constructor;
  console.log(_newTarget);
}

Actual behavior:

Compiles as:

$ tsc --target es6 test.ts
test.ts(2,18): error TS1109: Expression expected.

[basarat]

I think it should just be supported valid compile without getting into how to do a great emit.

That said window would be a bad idea (e.g. nodejs)

[kitsonk]

That said window would be a bad idea (e.g. nodejs)

Revised:

function Foo() {
  var _newTarget = this === (typeof window === 'undefined' ? global : window) ? undefined : this && this.constructor;
  console.log(_newTarget);
}

Foo();

When 'use strict'; is used, then this will be undefined anyways and the emit could simply be:

'use strict';

function Foo() {
  var _newTarget = this && this.constructor;
  console.log(_newTarget);
}

Foo();

[mhegazy]

duplicate of #2551

[kitsonk]

Ooops... sorry... I will move over to there...