Simple Calculator Class

Calculator.js

class Calculator {
  #numbers = {
    'zero': 0,
    'one': 1,
    'two': 2,
    'three': 3,
    'four': 4,
    'five': 5,
    'six': 6,
    'seven': 7,
    'eight': 8,
    'nine': 9,
  };
  #operators = {
    'plus': '+',
    'minus': '-',
    'multiply': '*',
    'divide': '/',
    'modulus': '%',
    'exp': '**',
  };
  #calculation = [];

  constructor() {
    this.__createNumberMethods();
    this.__createOperatorMethods();
  }

  __createNumberMethods() {
    Object.keys(this.#numbers).forEach(numberKey => {
      this[numberKey] = function() {
        this.#calculation.push(this.#numbers[numberKey]);
        return this;
      };
    });
  }

  __createOperatorMethods() {
    Object.keys(this.#operators).forEach(operatorKey => {
      this[operatorKey] = function() {
        this.#calculation.push(this.#operators[operatorKey]);
        return this;
      };
    });
  }

  clearCalculation() {
    this.#calculation = [];
  }

  getCalculation() {
    return this.#calculation.join('');
  }

  equals() {
    const calculation = this.getCalculation();
    this.clearCalculation();
    return eval(calculation);
  }
}

const calculator = new Calculator();

console.log(calculator.equals() === undefined);
console.log(calculator.one().equals() === 1);
console.log(calculator.one().zero().zero().equals() === 100);
console.log(calculator.one().plus().two().equals() === 3);
console.log(calculator.one().minus().two().equals() === -1);
console.log(calculator.two().multiply().two().equals() === 4);
console.log(calculator.one().two().divide().three().equals() === 4);
console.log(calculator.one().two().modulus().three().equals() === 0);
console.log(calculator.two().exp().three().equals() === 8);