TypeScript: Declaration of variables / attributes in classes / methods

Question

Can somebody give me answer to the following two questions:

1) Why isn't it possible to declare variables in methods like an attribute in the comprehensive class?

What I want: private foo: string (compiler error)
What I have to do: var foo: string (no compiler error)

2) When do I declare a variable as an attribute of the class and when do I declare a variable only in the method? I'm not sure if the Java knowledge fits in this case. Spontaniously I would say it depends on the scope of the variable (if it is needed f.e. in two or more methods -> attribute of class OR otherwise -> variable of a method).

Thank you!

Because variable created inside method have only one possible scope - method scope. — Fabio
– Fabio, Commented Nov 7, 2015 at 23:24

David Sherret · Accepted Answer · 2015-11-08 16:56:54Z

2

Answering you would be easier if you mentioned what you're trying to do.

TypeScript private class members aren't actually private at runtime; if you want actual privacy, you should use a closure like so:

class Foo {
  getSomethingPrivate: () => number
  constructor() {
    var somethingPrivate = 1;
    this.getSomethingPrivate = function() {
      return somethingPrivate;
    }
  }
}

edited Nov 8, 2015 at 16:56

David Sherret

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answered Nov 8, 2015 at 3:05

slikts

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