Transform class into constructor function

In the task, there is a class Test that needs to be transformed into a constructor function, preserving its properties and methods.

class Test {
  constructor() {
    this.a = 777;
  }

  say() {
    console.log(10);
  }
}

const res = new Test();
console.log(res);
res.say();

Rewrite this code so that instead of declaring a class, a constructor function is used, and methods are declared via the prototype or inside the function, as is common in the old JavaScript style.