Automagic data properties in JavaScript classes

[jrieken]

The ES6 spec for classes doesn't include properties making the code below valid JavaScript (and invalid TypeScript) code

class Cat { 
  constructor(name) {
    this.name = name;
  }

  speak() {
    console.log(this.name + ' makes a noise.');
  }
}

When feeding code like this into the TypeScript compiler you get an error about this.name not being defined. TypeScript should be able to detect that this is a JavaScript class (*.js,*.jsx-files) and (1) not mark the property access this.name as error and (2) offer tooling support for the data property (IntelliSense et al)

[danquirk]

We have another issue somewhere tracking adding support for this style of pattern (ie enumerate assignments to this in the constructor body and consider them instance properties implicitly) but I can't find it at the moment.

[billti]

#4790 covers this and other topics for better TypeScript inference of < ES6 style JavaScript.

[RyanCavanaugh]

#4955