privateProps.js

class Arithmetic {
  // inititalize the private property
  #value;
  
  // add getter for value
  get val() {
    return this.#value; // <== access the private property
  }
  
  // rest of the code truncated for clarity
}


a = new Arithmetic()
a.sum(1, 3, 6)   // => { value: 10 } 
  .subtract(3)   // => { value: 7 }
  .add(4)        // => { value: 11 }
  .val           // <== read the result of the computation