How to compile a TypeScript project correctly?

Question

typescript

There is the following code in TypeScript:

class A {
    a: string;
    b: number;

    constructor() {
      this.a = 'str1';
      this.b = 20;
    }
  }

  class B extends A {
    c: string;

    constructor() {
      super();

      this.c = 'str2';
    }
  }

  var a: B = new B;

  console.log(a);

I can run the compilation either directly through "tsc", or with the help of a collector, everything works fine. The next step is to separate the classes by writing them in different modules.

a.ts module:

export class A {
    a: string;
    b: number;

    constructor() {
      this.a = 'str1';
      this.b = 20;
    }
  }

index.ts module:

import {A} from './a';

  class B extends A {
    c: string;

    constructor() {
      super();

      this.c = 'str2';
    }
  }

  var a: B = new B;

  console.log(a);

This is where the problems begin. Compiling "tsc" in the browser gives an error:

exports is not defined

When using the collector - if I want to compile the result into one file, then I put the "module": "system" parameter in "tsconfig.json" - the following error appears:

System is not defined

If I put "module": "amd" - the error is this:

define is not defined

If I set "module": "commonjs", then it no longer accepts the "outFile" parameter, it compiles all ts-files separately. When connecting these files to the project, the browser gives the following error:

exports is not defined

Prompt the correct sequence of actions. It is advisable to set up the assembly of the project in one js file so as not to include each module in html separately.