1class Calculator {  
2  constructor() {  
3    this.value = 0;  
4  }  
5}  
6
7const calculator = new Calculator();  
8
9const operations = {  
10  add(num) {  
11    this.value += num;  
12    return this.value;  
13  },  
14  subtract(num) {  
15    this.value -= num;  
16    return this.value;  
17  },  
18};  
19
20Object.keys(operations).forEach((op) => {  
21  Calculator.prototype[op] = operations[op];  
22});  
23
24console.log(calculator.add(10));  
25console.log(calculator.subtract(5));